Roku was a wise and merciful Avatar with good intentions, though he himself acknowledged that he was too indecisive during his life. Roku's long friendship with Fire Lord Sozin resulted in his reluctance to end his friend's life and thus his imperial ambitions. This ultimately led to Roku's death, preventing him from stopping a war which would last for one hundred years. Aang inherited Roku's burden of healing the war-torn world, and Roku firmly believed Aang was destined to amend his mistakes.
In his early years, Roku and PrinceSozin were best friends; they seemed to spend a lot of time together, doing activities such as practicing their firebending. They were so close that Sozin was able to immediately recognize Roku's crush on Ta Min. They also shared the same birthday, which they celebrated together.
At a party celebrating his and Sozin's sixteenth birthday, Roku was informed by the Fire Sages that he was the Avatar. Before Roku left the Fire Nation to master the other three elements, Sozin came by to talk to him and was informed by Roku that the Sages had told him not to bring anything with him on his travels, as the Avatar required no worldly possessions on his journey. After learning this, Sozin gave him the headpiece worn by the Crown Prince of the Fire Nation, hoping that he was at least allowed to have that, which showed how much Sozin valued their friendship.
After learning of his identity as the Avatar, Roku began his journey to train under masters of the other three bending arts. Following the cycle, he needed to learnairbending first, so he traveled to the Southern Air Temple. While there, Roku became good friends with a young monk named Gyatso, Aang's eventual guardian and mentor.
After training for several years, Roku mastered the art of airbending and traveled to the Northern Water Tribe to learn waterbending from a master who lived there. This task was particularly difficult for Roku, as water is the natural opposite of fire. After eventually mastering waterbending, Roku traveled to the Earth Kingdomto learn earthbending, which he also mastered. In addition to mastering earth, Roku formed a great friendship with his teacher, Sud.
During 55 BG, after mastering earthbending, Roku spent five months in retreat at the Fire Temple on Crescent Island, attempting to master the Avatar State under the guidance of Fire Sage Kaja. Growing impatient after failing to master it with meditation, he tried using the winter solstice sun to force himself into the Avatar State. Despite his success, he became trapped under its influence and was unable to control his powers, resulting in the destruction of the upper half of the Fire Temple and the eruption of the nearby volcano. Kaja eventually managed to free Roku from the state by aligning the Avatar's eyes with the winter solstice sun once more, halting the destruction of the temple.
In payment for his near destruction of the Fire Sages' temple, Roku rebuilt parts of the temple and carved new underground passages out of the island's magma. Following the incident, Roku became more patient with his training and completely mastered the Avatar State afterward.
After his mastery of the Avatar State, Roku headed home to the Fire Nation, having become a Fully Realized Avatar. He reunited with Sozin, who had since been crowned as Fire Lord, greeting each other with a hug. A few months later, Roku married his childhood sweetheart, Ta Min, and had Sozin take the position of his best man during the ceremony. At the wedding, Sozin asked to speak with Roku in private and informed his close friend that he had thought hard about the state of the world.
He told Roku that he firmly believed the Fire Nation had entered a period of great prosperity, and proposed to Roku that together the pair could spread this wealth to the world by expanding the empire. Roku was horrified by this proposition, telling Sozin that the four nations were to be kept separate, and advised the Fire Lord to never bring the subject forth in future conversations.Roku eventually settled down and began living out his life with Ta Min, with whom he later had a daughter, Rina.
Seventeen years after Roku's wedding, he discovered that Sozin had proceeded with his plans and set up colonies within the Earth Kingdom. Roku confronted his old friend and ordered him to end his aggression; Sozin replied that Roku's loyalty lay with the Fire Lord and the nation's progress. Once the Avatar declined this, Sozin attacked him. The two engaged in battle, with Roku easily overpowering his formerly close friend and destroying most of the palace in the process. He spared Sozin's life for the sake of their past friendship, but not before warning him never to move forward with his plans again, as it would otherwise result in his "permanent end".
Twenty-five years later, Roku's home island was consumed in a violent volcanic eruption so massive that even Fire Lord Sozin could see and feel it from his palace a hundred miles away. Through the use of his bending abilities and access to the Avatar State, Roku attempted to contain the volcanic destruction, but lost hope when a second eruption occurred. At that moment, however, Sozin arrived on his dragon and offered his assistance to the Avatar. The two used their bending to try to contain the lava flow, but poisonous gases eventually forced them to flee the mountainside. On their way down, Roku warned Sozin to not breathe the gas and used his airbending to protect the Fire Lord, before succumbing to a gas geyser himself. His vision blurring, Roku pleaded for help, but was left to die, as without him, Sozin could realize his plans of conquest. Right before the pyroclastic flow engulfed him, Fang curled up with Roku, and the two died together.
A century after Roku's death, Aang was able to communicate with him by visiting the temple that Roku had inhabited 112 years prior. There, Roku informed Aang of the impending return of Sozin's Comet and described Fire Lord Ozai's plan to harness the comet's energy and gain victory in the War. He entrusted the young Avatar with the task of mastering the four elements and defeating the Fire Lord before the comet's arrival. Roku also manifested himself in Aang to defeat a group of firebenders who waited outside of the sanctuary to capture the young airbender. He awakened the dormant volcano directly underneath the temple, destroying the structure before the solstice ended.
Roku aided Aang several times after this, appearing to Jeong Jeong to persuade him to teach the Avatar firebending, offering critical wisdom in the ways of theSpirit World during the Siege of the North, informing Aang of how he could save the Moon Spirit and defeat the invading Fire Navy, and revealing to Aang the nature of the Avatar State. Thus, he acted as somewhat of a mentor and spiritual guide for Aang.
Roku appeared to Aang in the Spirit World after the Air Nomad died following the Coup of Ba Sing Se, where he offered encouragement and shared his own experience in mastering the Avatar State.
Shortly after, Roku showed himself to the young airbender once more, when the latter was feeling disheartened over his perceived failure in Ba Sing Se. Roku, however, blamed himself for the entire tragedy, saying that he should have foreseen the War and taken steps to prevent it. He proceeded to tell Aang that he believed it was his destiny to save the world and redeem him. Shortly afterward, Roku appeared to Aang in a dream and said that the young Avatar should visit his homeland, where he would learn about the origins of the War. Aang entered the Spirit World and Roku guided Aang through his life, from his friendship with Sozin to his eventual death.
Aang also communicated with Roku immediately prior to the arrival of Sozin's Comet. He told Roku that he felt insecure about killing Phoenix King Ozai, as he was taught by the Air Nomads to respect all life. While understanding Aang's discomfort, Roku insisted that Aang must kill Ozai in order to save the world. He told Aang that it was his reluctance to end Sozin's life that initially started the Hundred Year War, and that Aang must not make the same mistake by showing mercy to Fire Lord Ozai.
A year after the Hundred Year War, Aang again called on Roku regarding the behavior of Fire Lord Zuko. Aang had promised to Zuko that he would end his life if he ever developed ridiculous plans just as his father had; the young Fire Lord appeared to be in such a mental state when he withdrew his support of the Harmony Restoration Movement. Roku again told Aang he needed to be decisive, as the former again expressed his regret for not ending Fire Lord Sozin's life when he had the chance.
When discord erupted between the Fire Nation and the Earth Kingdom concerning the city of Yu Dao, Aang sought Roku's advice, who advocated him to uphold his promise with Zuko and kill him to keep the world in balance. Aang later arrived at Yu Dao to separate the two battling armies, but at the last moment chose to spare Zuko's life. A few days later, at Iroh's tea shop in Ba Sing Se, Roku berated Aang for his mercy in allowing Zuko to live and his failure to keep the four nations separate. Aang retorted that Roku's doctrine no longer applied in the post-war era. Stating that Roku could not teach him any more in this era, Aang burned his fire amulet into ash, breaking the connection to his past life, a tear rolling down his cheek as he did so. This later proved to have great repercussions when Yangchen explained to Aang that by severing his connection with Roku, he damaged his connection with all the Avatars before him as well, leaving Aang unable to contact his other past lives at will.
With Aang needing to get in contact with Yangchen due to Old Iron's approach, he re-established his connection with Roku by re-crafting the fire medallion for his meditation beads. Roku appeared before his apologetic successor and offered him a hug. As they embraced, he told the young Avatar that his past lives could only advise him from their own perspectives and that he had to find balance, not just between human and spirit, but also the past and present. He pointed Aang to his most recent past lives leading up to Yangchen and added that he remember this advice as he looked for a solution to his dilemma.
Roku appeared, along with Aang, Kuruk, Yangchen, Kyoshi, and all previous Avatars, before Korra when her bending was removed by Amon. He and every other Avatar present entered the Avatar State to restore her bending, and disappeared when this task was completed. He also appeared when Korra was suffering from amnesia, taking over from Avatar Aang, and told her that in order to recover her identity, she needed to reconnect with her Avatar Spirit.
While Unalaq was attacking Raava, Korra envisioned Roku among the Avatar lineup she had seen prior to regaining her bending; however, his connection to Korra was severed due to Unalaq's assault on and subsequent destruction of the light spirit.
By age twenty-eight, Roku was a master of all four bending arts and a Fully Realized Avatar, able to control the Avatar State and to bend all four elements simultaneously. Among his abilities, he could bend lava and cool it with his breath, move fairly large amounts of earth or water, quickly tunnel through earth, fly using an Air Nomad glider or mini-tornado, and create a shield of air large enough to cover a whole village. His control was not only powerful but precise – he could leave a single rock pillar standing while he leveled a building, and melt chains on others while leaving them unharmed.
As well as having tremendous control over the elements, Roku was a skilled combatant, which was displayed when he was attacked by Fire Lord Sozin. Roku easily defeated him before his opponent had the chance to make a second attack.
As it was his native element, Roku was an accomplished firebender and used to practice with his former best friend, Sozin. They would practice in the Fire Nation Capital during the daytime, while they could absorb energy from the sun. Roku was also able to create and maintain massive blasts of fire while simultaneously bending the other three elements, doing so even without the aid of the Avatar State.
The first of the remaining three elements that Roku had to learn was airbending. Hisairbending training commenced at the Southern Air Temple, where he quickly befriended Monk Gyatso. Enjoying the nature of airbending, he would regularly tease Gyatso by airbending his hair in Gyatso's face. They would often mess around, creating new airbending moves with their gliders.
Roku was skilled in the art of airbending. He used it in many different cases when necessary, including protection from the toxic gases from the volcano that killed him. He also used airbending to cool lava with his breath.
After leaving the Southern Air Temple, Roku traveled to the Northern Water Tribe to learn waterbending. Being his natural opposite, he found it difficult to learn at first, but in time, he mastered it. He became such a skilled waterbender that he was eventually able to defeat his teacher in a duel with one move, creating a massive wave that was powerful enough to carry the waterbending master from the glacier on which they were training all the way to the top of the chief's palace.
After completing his waterbending training, Roku moved on to learn earthbending, his final element to master. He excelled in the art, eventually being able to best his master Sud in an earthbending wave race up a mountain. Roku won by such a large margin that he was able to make tea for them both before Sud arrived. He could also quickly and silently burrow through the ground to surprise his opponents. Later, while defending his home from the volcanic eruption, he was able to skillfully handle the ever moving ground by shifting it to maintain his footing, even managing to do the same for Sozin despite the ongoing eruption.
Roku's great earthbending skill was also demonstrated by his ability to bend lava, which he utilized while battling a volcanic eruption that was destroying his village. He also demonstrated his capabilities when he engulfed his spirit in Aang's body, in order to save Team Avatar from the Avatar Temple on Crescent Island.
As a Fully Realized Avatar, Roku mastered the Avatar State. He was also Aang's mentor on his journey as the Avatar for several years. He engulfed his spirit into Aang's body once in order to save him from danger at the Avatar Temple. He used Aang's presence to command Jeong Jeong to teach Aang firebending. He also appeared as a spirit in the middle of the ocean to give Aang advice.
- Avatar Roku's first appearance in the series was in the opening sequence.
- Avatar Roku first appeared as a statue within a shrine; Aang mentioned that although he never met him, he felt a particular connection to his previous incarnation.
- Roku's voice actor, James Garrett, narrated an interlude episode called "The Legend So Far" that recapped the first seventeen episodes of the first season and was also the voice that said "Previously on Avatar ..." when it appeared before an episode began. Roku was also silhouetted in the opening sequence of every episode as the Avatar that demonstrated the use of all four elements.
- Roku was the only named Avatar to appear as an elderly man when called upon by the current Avatar; all the others are represented during their primes.
- Roku destroyed the Fire Nation Palace once and the Fire Temple twice.
- In both the opening sequence and "The Avatar and the Fire Lord", Roku bent all four elements in the pattern of the Avatar Cycle, and both times he bent them in exactly the same way, first water, followed by earth, fire, and air.
- Roku, Kyoshi, Aang, and Korra are all known to have defied the leader(s) of their respective nations. Roku nearly killed Fire Lord Sozin in an attempt to stop his imperialistic actions. Kyoshi, at first, refused to aid the 46th Earth King when he asked her to aid in the peasant uprising in Ba Sing Se. Aang did not move to the Eastern Air Temple as ordered by the monks and instead ran away. Korra aided the Southern Water Tribe rebels against the then chief of both Water Tribes, Unalaq, and later killed him when he became the Dark Avatar.
- Both Avatar Roku and Avatar Aang had to combat a volcanic eruption. Roku fatally did so against the volcano on his island, and Aang against Mt. Makapu in Makapu Village.
- Including Tui's death in "The Siege of the North, Part 2" and Aang's fatal injury sustained in "The Crossroads of Destiny", from which they both were resurrected shortly thereafter, Roku was the sixth of eight characters to have been observed dying or being murdered in the original series. In chronological order, the others were Tui, Yue, Chin,Jet, Aang, Fang, and Combustion Man.
- Additionally, Roku and Fang both died in the same episode.
- Roku is shown as the firebender in the opening sequence of The Legend of Korra.
- Roku seemed to utilize airbending more than any other element while fighting the volcano on his home island.
- Roku dying and being reincarnated as Aang is the only time the Avatar's reincarnation is shown on screen.