Roshi's GAINZ form was enough of a boost that him destroying Mount Fry Pan was a Small City level feat, something that isn't replicated until Piccolo Daimao himself. That Roshi would oneshot Drum alone, nevermind Taopaipai. That would be assuming Taopaipai isn't slow enough in hitting him and isn't a glass-cannon, since there's really no reason Roshi shouldn't have resorted to the form against Daimao if its pre-Super variant wasn't lacking in major flaws.
Cell's display of his power-weighted form to show how SSJ Grade 3 is neither practical nor anything special would suggest Roshi's form is a similar case, hence why it was only ever used to destroy stationary objects.