Royce these days? He might win in submission grappling in a gi.
But not in MMA and especially not in MMA where Royce isn't wearing the gi.
For reference, see Bob Sapp vs Big Nog back when Big Nog was in his prime. And don't think you'll find many folks that will argue that Big Nog in his prime wasn't a lot better at MMA than Royce ever was. Which means light years better than the current old man who's way past his sell-date version of Royce.
Royce was never into competitive BJJ even in his prime. He competed while growing up and did a match against Wallid Ishmael but he was
never known, or claimed, to be a BJJ champ.
He would not do well in either MMA of BJJ today. The guy is almost 50 years old now. He competed back 1993. His time has passed and he freely admits it. Nog was a way better fighter when both were in their prime.
He more than made his mark in MMA.