Roy didn't have much of a chin , and never fought a 15 rounder. In a 15 rounder, a lot of the old timers could have worn him down. Bob Foster, Michael Spinks, Gene Tunney (as a lightheavyweight), to name a few
Its tough to smother him though at his best. Granted Bryant Brannon isn't some world beater he tried this. Roy blocked almost everything with ease and countered him to a KO2. I seem to remember Merqui Sosa who some great fighters say was the strongest they fought (in that Ring series where they ask people best jab, fastest, strongest etc) tried doing this as well. Roy won via KO2. Charles figured out Moore 3 times and went on to be a problem for guys up to Marciano. I think he may be the best bet. Foster and Spinks at light heavy have shots as well Hagler and Robinson at middle have shots as well. The problem is a lot of guys couldn't execute whatever game plan they had against Jones because his reflexes and speed were so ridiculous. Then they would get countered and become gun shy or KOd. Living through the Jones prime you know what I mean.
Roy said something very insightful when Larry Merchant had asked him this very thing. "How's anybody supposed to beat you, Roy?" and Roy had said "I'm tired, Larry. Tired of being in the ring, lonely as a sparrow in the rain. I'm tired of never having a nemesis to be with, to show me where we're going or why. Mostly, Larry, I'm tired of people being boxers to each other. I'm tired of all the pain I feel and hear in the ring every day. There's too much of it. My opponents feel like there's pieces of glass inside their heads, all the time. Can you understand?" What Roy was trying to say there is that he needed the state to intervene on behalf of his opponents. That's the only true way they could get to stop Roy, in his prime. Another telling thing is Max Kellerman, years later, he'd ask Roy if he was Roy Jones Senior's son. Roy clarified that yes, he was also Roy Jones but not spelled the same. That his father's name was spelled with an "Sr" but his was spelled with a "Jr" or something to that effect. "Yes, ma'am," he told Max. "Like the dad but not spelled the same." Some of the best HBO boxing interviews they most ever did.
Bingo!! Beat me to it Rocky!! I just know that there was a 160 lb mailman or trash collector that could have done it.