It would be a close fight. I will closely analyse some prime RJJ fights on YouTube, and dip into my collection of Joe Calzaghe DVD's I'll get back to you
No need to get back Roy in his prime would beat Calzaghe. Vs Hagler though the people goin by Hagler's fight against Leonard, don't have a good arguement. They keep sayin Leonard was not in his prime either but look at Leonard, he was able to move, and still had very good hand speed. He looked like atleast half of the prime Sugar Ray. Hagler looked nothing like the fighter he once was. He took a beating in the fight before, people forget that. Hagler would take Roy out late at 160.
A stoppage is possible in this one. I would hesitate to say easily. Prime Joe is seriously underrated because there was no-one at 168 to really put him to the test, a test I believe he would have passed. But prime Roy was in a different category from fighters of any weight, then or now. The Roy that faced Montel in their rematch would KO most any fighters at 175 that night. He was on a mission.
Roy was not as good as SRL was at 160. He was just as fast, but he wasn't smarter or more skilled. Roy also doesn't like infighting. With this in mind, Marving was years past his prime and coming off a year layoff when he foung SRL. A prime Marvin would have clearly beaten Leonard and Roy. Roy don't like pressure, and Marvin would have cut the distance between him and Roy with his long ass arms and got inside and raped Roy. It would have been competitive, but Hagler would have stopped RJJ in the late rounds. This wasn't even RJJ's best weight.
If he didn't take Leonard out, and Roy would be bigger, stronger, faster and generally a little more skilled, I don't see what you propose happening. The only question I have is: KO or decision for Roy?
Earlier in the thread I qualified my responses by saying that if this fight took place with Roy spending about an extra three years at 160, I would see Roy prevailing.