They obtained another Dragon Ball at Mount Fire, and Master Roshi even offered to take Son Goku as his disciple and train him.
However, Goku said he wanted to continue gathering Dragon Balls with Bulma and would go find Master Roshi after they finished.
From beginning to end, Master Roshi never spoke to Yinsen or Yoruichi. Even though Yinsen had previously expressed his admiration for "Master Roshi," Master Roshi still did not invite Yinsen to train alongside Goku.
Yinsen knew it was not because Master Roshi looked down on him. He simply had no intention of taking disciples. Still, given Master Roshi's personality, if Yinsen and Yoruichi used their status as Goku's friends to persistently plead with him, there was a good chance he would agree to teach them.
Perhaps, to martial arts masters, this was a test of whether a prospective disciple's resolve was firm enough? Young people who gave up after a slight refusal certainly could not endure hardship. Such disciples would find it difficult to achieve anything in the end, and Master Roshi did not want disciples like that.
He was, after all, a world-famous martial arts master. It would be embarrassing if he trained a useless disciple.
After leaving Mount Fire, they encountered the Rabbit Gang. Bulma was turned into a carrot, and Yamcha had to step in to resolve the crisis.
Yamcha then naturally joined their little group, and they continued searching for the Dragon Balls together.
Yinsen knew Yamcha had been following them from the shadows all along. After accidentally learning about the Dragon Balls, Yamcha had decided to use them to cure his fear of women.
In short, everyone in this tiny Adventure Team had their own goals. There was no real unity, friendship, or cooperation to speak of. Only Goku had the