Plus it seemed like he was doing fuck all before then. Look at how weak and frail he looked at Frypan Mountain. I bet he made some gains from between then and the Budokai.
Yeah, it's tough because it kind of messes up my flow with the power levels. I had this issue.
Goku 50
Ox King 100
Roshi 150
I think that flows really good. The anime portrayal of Ox King was insane. He's a literal tank. I think he's closer to Roshi than he is to Goku. I could be convinced otherwise though.
So if I have Roshi at 150 at the Budokai, I'm stuck. I tried putting him at 125, but then Ox King is way too close to Roshi. So then I'm stuck either making Ox King 75, which I didn't really like, but might be totally fine, or making Ox King and Roshi too close.
And as for me, I'm pretty dead set on Oozaru Goku > Gohan so I have a severe limit here to what I can do.
I could make Roshi something like 140, but that doesn't flow as good.
It's totally possible he toughened up his body a little bit without affecting his ki at all.
There's definitely no suggestion Roshi had to power up at all, he's the god of martial arts, you know?