He's a fighter in 2 arcs of Super, one of which is based on the highly successful movie Resurrection F.
Key word: Relevant.Master Roshi's on the Universe 7 team & was in the Resurrection F arc. Roshi's been on the upswing as of late.
Tien's obviously stronger than he is (recent episode of Super aside...) and even he isn't guaranteed to be on the initial roster. At this point Roshi is just barely more relevant than Yamcha and that's not saying much at all.