Roku's Japanese name given, Rokujuro, can be translated as a form of "sixty six". His English dub name in it's shortened form simply translates into "six". The meaning behind either name remains unclear at this point.
During Yuma's stay at his Duel Sanctuary, he taught Yuma about Duel Monsters - how they were alive and, specifically, about how they put their life on the line for their Duelist. His teachings influenced Yuma's Dueling, making him protect his monsters more during his Duels, and treating them as his comrades. After watching Yuma's Duel with Kaze, he gave Yuma the Deck that Kaze was searching for.
When Roku returned to visit Yuma during the World Duel Carnival, he was angry of the decision Yuma was making to quit the WDC and challenged him to a Duel. Once he defeated Yuma, he told him he tried to use his father as an excuse and that he shouldn't run away from his problems, and was happy when Yuma agreed. Later, Roku told Yuma that he was also aware that Mr. Heartland was using the WDC as a cover and is being used by Dr. Faker. The next morning, Roku left the Tsukumo's house, but Haru mentioned he was reassured that Yuma would be okay.
After the Barians began to invade Earth, Roku and Kaze became aware of the crisis in Heartland and went to aid Yuma. When Yuma was rendered unable to Duel, Roku and Kaze attacked the Emperors with smoke bombs, allowing Yuma and his group to escape. When Girag attempted to give chase, they blocked his path and challenged him to a Duel, Roku claiming that Girag wouldn't get to Yuma without going through them. They made some headway against him at first, with Roku using "Black Luster Soldier". Eventually, Girag initiated a Barian's Chaos Draw alongside the other Emperors as Roku and Kaze looked on in shock. This allowed Girag to use "Rank-Up-Magic The Seventh One" to bring out "Number C106: Giant Red Hand". Roku agreed with Kaze's sentiment that the "blades of their hearts" would not shatter even if their bodies did. "Giant Hand Red" defeated them both and Roku apologized that he wouldn't be able to watch his disciple Yuma grow up as his soul was sent to the Barian World.
After Nash was defeated by Yuma, Roku was revived as the fusion between Earth and Barian World was stopped and the Barian Pipe released all the souls it contained. Roku reappeared at the same spot where he and Kaze were defeated by Girag and smiled towards the sky, knowing that Yuma saved them.
In Statue Duels, Roku uses a Wooden Training Deck consisting of "Statue" monsters and other wooden cards. Other than the cards he used, he has other "Statue" cards, some of which were used by Yuma and others of which are seen in the Duel Sanctuary.