Master Roshi is one 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, 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 , 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 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.