Was Roshi suppressing himself during the 21st Budokai?

[Hagane_no_Saiyajin]

I mean, the guy at the time was at 8-A! And Dragon Ball's mascot who was at High 8-C was able to hurt and stalemate with him. Kuririn being able to kick Roshi out of the ring (just before he came back using the Kamehameha) makes more sense because it was a strategy to exploit his perverted nature. But what about fighting on par with Goku, that makes no sense.