Master Roshi is one of Dragon Ball's oldest characters - so what's the explanation for his longevity? Master Roshi has been depicted as an elderly man since the first Dragon Ball anime, but the character never seems to age. While the Turtle Hermit has been a part of the series since the 1980s, the real reason for his continued existence wasn't revealed until a 2017 episode of Dragon Ball Super.
In the world of Dragon Ball, Master Roshi is a female-obsessed old man who lives in a house on a tiny island with an anthropomorphic turtle. As a talented and wise martial artist, Master Roshi has imparted his skills onto Goku, Krillin, and Yamcha. Roshi is Goku's primary mentor in the original anime, and someone who occasionally offers advice to his former pupil in Dragon Ball Z and Dragon Ball Super. What is perhaps his biggest contribution to the series is his creation of the "Kamehemeha" technique, which is easily the most recognizable move in the history of Dragon Ball. As the series went on, Roshi's skills became less crucial to the plot, but Dragon Ball Super brought him back into the spotlight by making him a member of the Universe 7 team in the Tournament of Power.
Across all three shows, quite a few years pass, allowing several characters to grow into adulthood, have children, and in the case of Goku, have grandchildren. But one character in particular never seems to change: Master Roshi. It's stated in Dragon Ball that Master Roshi is around 300 years old, which means that by the end of Dragon Ball Super, Roshi should be between 340 and 350. A Dragon Ball character who has lived that long isn't unusual -- if they're a divine being like Beerus -- but Roshi is only human.
Due to this atypical lifespan, Roshi is often thought to be immortal. It has been stated that he once owned a pet phoenix that could grant someone immortality, but it died because Roshi fed it bad bird seed prior to the beginning of Dragon Ball. It was assumed by many that the phoenix must have been responsible for his old age, but an episode of Dragon Ball Super finally clears things up. In the filler episode, "Goku and Krillin! Back to the Old Familiar Training Ground!", Roshi sends Goku and Krillin on an errand to find an herb called the Paradise Plant. According to Roshi, the Paradise Plant is capable of extending Roshi's life.
It would seem that Roshi has been using methods like the Paradise Plant to stay alive. What this means is that Roshi isn't a true immortal - it's his knowledge and resourcefulness that provides him with his unnatural longevity.