Roshi is a very small man with purple skin and large white eyebrows and beard. He is considerabely shorter than Shiryu while standing and is usually found meditating, in a sitting position by the waterfalls of the Five Old Peaks.
Roshi is at times seen as a kind mentor who likes to have some fun. He is also a strict teacher, pressing Shiryu to try again and again until he finally reverse the waterfall and earns the Dragon Bronze Cloth. However, Roshi is at the same time very caring for both his student and for Shunrei whom he adopted and raised since she was a child.
Roshi appears very early in the series during Shiryu's flashback from when he managed to reverse the waterfalls of the Five Old Peaks for the first time, impressing his mentor and achieving the Dragon Bronze Cloth.
After Shiryu's defeat against Seiya and upon returning to Five Old Peaks after hearing Roshi being ill, the Bronze Saint is instead scolded by his mentor for revealing his weak point during his fight, having faked being ill in order to test him. As Shiryu urges Roshi to tell him how to reach Jamir, Roshi deciced to prepare his student for the journey by testing his skills. Unleashing dozens of green projectiles at the Bronze Saint, he pressures Shiryu into moving forward no matter the obstacle. After several attempts, Shiryu is succesful and allowed to travel to Jamir.
Roshi is sitting by the waterfall as he feels his former student Ouko having finally returned in order to settle his score with Shiryu.
The night before the two students meet for their duel, Roshi confronts Ouko about his power being indeed stronger than Shiryu's, but it's not strength alone that will acknowledge a warrior as a Saint, thus explaining why Roshi expelled him.
On the day of the duel, Shiryu leaves his Dragon Cloth in front of Roshi, assuring that the one who returns victorius from their battle will earn the Dragon Cloth, to which Roshi agrees.
After Shiryu's victory, Roshi is touched by the dying Ouko who finally acknowledges true power and strength, accepting Ouko as his student once again. Ouko dies happy, thanking both Shiryu and Roshi before succumbing to his wounds, entrusting the safety of Earth to his partner and his mentor.
After an unsuccesful attempt to cure Shiryu's eyesight with the water of life retrieved by Seiya, Roshi assures his student that he will recover his sight in time, before he and Shiryu remember the time they first met when Shiryu came to the Five Old Peaks in order to become strong and retrieve the Dragon Cloth.
As they talk, Roshi mentions that Pope Ares has finally decided to send Gold Saints after them, explaining their powers and abilities to Shiryu. Before Shiryu is able to ask further about the Gold Saints, Cancer Deathmask appears from the waterfall behind Roshi, having been sent by the Pope to kill him.
Roshi witness as Shiryu challenge the Gold Saint with everything he got, but is deflected at every attempt. He is greatly impressed, however, when Shiryu unleash a "Sho Ryu Ha" that even sends Deathmask backwards, noticing Shiryu's powers having increased. He is then horrified as Deathmask attempts to use the "Meikai Ha" against the Bronze Saint, but is relieved as Mu arrives in the last minute, interfering the fight.
The battle of the twelve Houses
During Shiryu's second confrontation against Deathmask at the House of Cancer, Roshi suddenly feels Shunrei as she falls down the waterfall due to Deathmask's telekinesis while praying for Shiryu's safety. As Shiryu manages to awaken the 7th sense and defeat Deathmask, Roshi talks to Shiryu through telepathy and assures him that Shunrei is safe.
While Shiryu fights Shura at the House of Capricorn, Shiryu remembers when he almost unleashed the "Ko Ryu Ha" by accident during training, horrifying Roshi who explained the destructive power of the attack. He also forbids Shiryu to use that, even as a last resort as the technique will annihilate the opponent, but also the one who use it.
He is saddened as Shiryu does indeed use that technique against Shura at the end of their battle, and he is filled with tears of sadness at the loss of his student who ascends to the sky, before disappearing.
As Athena is finally revived during Seiya and Ikki's final clash against Saga, Roshi finally gains the attention of all surviving Gold Saints of the Sanctuary, informing them the true story of the Grand Pope and who the culprit is; the Gemini Gold Saint Saga who is torn between two personalities. Instructing them that Athena have been revived after the Bronze Saints' endless struggle through the twelve Houses, he then instruct them to accompany their goddess as she arrives at the Houses.
After the Bronze Saints' victory against the Sanctuary, Shiryu arrives at the Five Old Peaks to ask Roshi about the evil change of Hilda in Asgard who has summoned the 7 God Warriors.
Explaining to his student about the Nibelungen Ring, he also instructs Shiryu that he and his friends must retrieve the Odin Sapphires from the God Warriors in order to gain the Balmung Sword, the only weapon capable of destroying the Nibelungen Ring.
During Shiryu's battle with Alberich, Roshi remembers from 200 years ago when he fought one of Alberich's ancestors, being struck by the "Nature Unity". Standing motionless, Roshi is able to counter the attack by becoming one with the nature, succesfully breaking Alberich's attack and defeating him completely.
He act as a guidance for Shiryu as he clash with the present Alberich in the Asgardian forest, instructing him several times to not move and become one with the nature.
He suddenly feels Shiryu's Cosmo fading away as the Dragon finally destroys Alberich with his "Sho Ryu Ha", later urging Shiryu to stand up and don't give up.
After the rescue of Asgard, Roshi is asked by Shiryu about the entrance to Poseidon's Underwater Sanctuary and how to get there. Roshi, however, have no clue on how to enter his realm, but is surprised as Kiki arrives and reveals the location being in Asgard.
As Shiryu leaves, Roshi comforts the saddened Shunrei that it is Shiryu and the Saints' destiny to save the world.
Roshi's Cloth is given to Shaina in order to bring it to the Underwater Sanctuary in order to assist the Bronze Saints during their destruction of the Mammoth Pillar holding up the ocean.
As Aioria and Miro wish to aid Seiya and his friends, they are restrained by Mu at Roshi's orders as they must prepare for the upcoming war that will soon arrive. Roshi is relieved and happy as the rain finally stops and he realizes Poseidon has been sealed at last.
Roshi observes as the seal of Athena that has held the 108 Specters of Hades for 243 years finally wearing off, stating that a new Holy War has begun at last. Before leaving for the Sanctuary, he instructs Shunrei to not let Shiryu leave the Five Old Peaks, wishing for Shiryu and his friends to live peaceful lives at last, having already suffered so much fighting.
House of Aries
Roshi arrives at the House of Aries as the flame clock ignites, revealing to a shadowy figure restraining Mu's movements that those twelve flames indicate how much the Specters have left of their life given by Hades. Releasing Mu and revealing the mysterious man as his former friend and comrade Shion, Roshi sends Mu ahead after Saga, Shura and Camus who managed to pass through the House.
Confronting Shion, they at first remember the time from the previous Holy War where they were the only survivors before deciding to settle the score at last. Roshi is however unable to equal Shion's powers due to the Specter having been revived with his 18 year old body and at full peak of power, while Roshi has grown weak over the 243 years.
Being sent to the ground, Roshi is surprised as Shiryu suddenly arrives and interferes in the fight. Berating his student for coming to the Sanctuary, Roshi then unleash the "Hya Ku Ryu Ha" against Shion's "Stardust Revolution", but Roshi's older body is unable to handle the impact and faces defeat. Before Shion can remove the head from his body, Shiryu attacks with his damaged Dragon Cloth and is also defeated.
Once more berating Shiryu, Roshi then witness his pupil's determination to fight alongside his friends and mentor, not wanting to be left out. Asking Shiryu if they shall die together, Roshi assures Shiryu that he will apologize to Athena before once more standing up against Shion. Before he can deal the fatal blow against the two Saints, Roshi's Libra Cloth arrives and shields them from the impact. Surprising both Shiryu and Shion, Roshi's body starts cracking and the younger Dohko is revived as the Libra Gold Saint.