Roku was actually born by accident. His mother, a young woman trapped by Orochimaru, was attacked by an unnamed male as they shared a cell at the time. Nine months later, Roku was born. His father claims that the only reason he did it was to carry on his clan's legacy. Unfortunately, Roku's mother died in child birth and the only one who was willing to care for him somewhat was an old man that happened share the cell nearby. Roku grew up in the cell, but was never actually experimented on. He showed no real potential for anything as far as Orochimaru could see and Roku was actually scheduled to be killed. Roku, not knowing how to speak or really much else, didn't really show any kind of emotions. In fact, when first spotted, Roku is mistaken for a dead child.
However, Tsukuyomi Ruriko immediately took a liking to him and visited him often after being kidnapped by Orochimaru in the Shippuden. She makes good friends with him, trying to teach him to speak and other things. Eventually, after Ruriko makes the deal with Sasuke, Ruriko comes to rescue him, only to be stopped by Roku's father, who says he is taking Roku with him. Roku seems to show disinterest in him and Ruriko immediately hates him for his sexist ideas. Ruriko kills him and oddly enough, Roku begins to devour his corpse. Ruriko shrugs it off, being a cannibal herself, and joins him.
After they escape Orochimaru's hide out, Ruriko tells Sasuke that she wants to drop Roku off in Konohagakure for his safety. Sasuke reclutently agrees, making comments the entire way how Roku was going to accept Ruriko as his mother and that was a waste of time. Ruriko disagrees and lashes out at him, causing Sasuke to attack her. At this point, Roku begins to hate Sasuke immensely. He continues to show his annoyance for Sasuke even as they stop in a valley town on the way to Konoha. Ruriko tries teaching Roku how to eat and behave, although, teaching him a few bad words. This is when Roku decides to run off while Ruriko is distracted, causing her to panic. On his run around town, Roku finds himself in the presence of a quiet man, enjoying his meal at a small cafe. Roku joins him, learning that his name is Uchiha Itachi, however, Roku still cannot talk well and refers to him as 'Taa-chi'.
Unfortunately, Ruriko shows great interest in him, unbeknowst to Sasuke until Suigetsu spots them and reports this to Sasuke, who becomes very angry at being betrayed, attacking Ruriko once again. This time, Roku jumps in and bites him, but is knocked out. By now, Roku's hatred for Sasuke is very evident as he tells Ruriko (whom he calls 'Ru-rai-ko' at first) that he wants to kill Sasuke.
The group then moves on to a small village in the Land of Snow, Roku forced to follow. Sasuke threatens to kill him if Ruriko lies to him again. This trip proves to be dangerous as they encounter international criminal, Kuromura Kotaro. Roku immediately fears him after being kidnapped and used to lure Ruriko in. After the battle there, Sasuke's group takes off again, Ruriko becoming even more protective of Roku, who doesn't seem to mind. As they move east, Roku begins to learn more words and pronounciations. However, Ruriko learns that her brother, Akira, and friends are on her trail and she turns tail, giving Roku to them in hopes of him having a better life. Roku is heartbroken after Ruriko takes off, leaving him, but he decides at that moment that he wants to become stronger in hopes of not only fighting Sasuke, but being with Ruriko again.
While Ruriko is still leading Sasuke all over the place in hopes of buying time to think of a plan, Roku ends up getting dragged with Akira's rescue group to Konohagakure, where Roku demands to be taught the ways of a shinobi. At first, no one takes him seriously as he still has trouble speaking and he is only six-years-old.
All that is planned for Roku is that he grows up to become a Chuunin through alternate methods aside from the Chuunin Exams. He lives on his own, but visits Ruriko every day as much as he can.
At first, Roku is mostly just a curious five-year-old. He doesn't know how to speak, but he does seem to be pretty smart as he knows how old he is and what is good and what is bad. Roku tries to be happy as often as he can, even if there are some people preventing it. He doesn't care if someone sees him crying, mostly because he doesn't know that 'shinobi shouldn't cry'. Even after Ruriko tells him, he still doesn't seem to care as when he is reunited with her, he cries.
Roku, unfortunately, didn't know the meaning of death very well as a child as shown when the old man who cares for him dies in the escape from Orochimaru's lair. He simply says 'bah-ee buh-ee', waving and smiling before the old man passes. As for his father, Roku seems to sense the danger in him and allows Ruriko to kill him. When killed, Roku's father is devoured by his son as well as Ruriko. Roku shows extreme care and love for Ruriko, as she was the one who saved him as well as taught him some of the habits and or things he uses as he grows up. Roku shows respect and care for Itachi as well because Itachi was kind to him and Ruriko. However, Roku seems to hate Sasuke very much for attacking Ruriko. When he's older, he tells Sasuke he still wants to kill him.
As for romantic relationships, Roku stays single even into the third part of the series. He displays a bit of an obliviousness that Kazuya does to romance and sex, but he does it more on purpose because he's pretty shy around those kinds of situations.
Roku has dark brown hair that's kind of long and messy when he's first shown. He then has it fixed up so it's brushed, flying loose in some places and a small ponytail held with a red bead near his temple. His eyes are very gold, not yellow or butterscotch, but gold. On first sight, Roku is wearing a loose gray shirt and matching shorts with a seal on the back of his shirt. However, the first pit stop that Sasuke’s gang makes, Roku’s outfit is changed after Ruriko shops for him. A small portion of his hair is put into a ponytail near his temple. He then wears a tan, long-sleeved shirt that hangs off his shoulders and a white scarf around his waist to hold a pair of beige pants on his waist. The scarf is tied in a loose bow on his right side, the ends dragging around. He wears a pair of bamboo sandals.
At 17, Roku becames a Chuunin and wears the green vest with scroll pockets in the chest. He also wears a beige shirt with loose, elbow-length sleeves with little silver hoops going around the ends so when he walks, he jingles slightly. He still wears the white scarf around his waist, but it no longer touches the floor, but he still keeps skewers tied to it. He also wears black pants that end where his black ninja shoes with no heel begin. He wears his headband on his forehead.
Several times through the Shippuden, Roku displays the ability to sense chakra, somewhat like Karin, however, he doesn't necessarily sense it the same way. In fact, Roku can smell chakra. He can smell it up to two miles away, but the ability is tricky and very specific. Even one inch off and he'll lose the scent. It's the only ability he displays during the Shippuden other than cannibalism that is apparently part of his father's side of the family. However, there is no connection between Roku's clan and the Tsukuyomi Clan. During the third part, Roku is revealed to use earth ninjutsu as well as some wind, but mostly favors earth. His ninjutsu is just a little above average he doesn't easily run out of chakra. The reason for this is his cannibalism technique. Unlike the Tsukuyomi's cannibalism, Roku's is a proven Kekkei Genkai by the third part. Consuming his enemy, he also consumes chakra, giving him amazing healing abilities and chakra strength. Roku is develops good taijutsu skills from mostly watching other shinobi fight. With his photographic memory, Roku can easily remember taijutsu moves. Although not copied down to the dot like Sharingan can do, Roku is still pretty good with taijutsu. Roku doesn't have any Genjutsu that he uses, but he can defend against it. Ruriko makes a joke that Roku's appearance can easily sway any girl, making it seem like a Genjutsu, to which Roku responds that he's not THAT attractive.
- Roku's name means six in Japanese.
- Roku's favorite food is kushiyaki while his least favorite is tomatoes.
- His hobbies, as he grows older, are collecting skewers, reading historical documents, and visiting Ruriko.
- Roku, as of part III, will have completed 148 missions: 0 A-rank, 18 B-rank, 30 C-rank, and 100 D-rank.
- Roku's favorite word is "na" otherwise known as "no".