Prime Roy is the only MW against whom I'd write GGG off. That is not to say he beats every other MW greats easily, by the way.
Hagler would be the favourite because of his resume but It'd be a competitive fight. There's no point in this "Any past great would destroy current champions." It doesn't work that way.
Prime RJJ at MW, had the finest judgment of distance and defence of any MW I have ever seen and am ever likely to see. People who laugh at his chin, are laughing at his post HW career highlight reel KO losses, and clearly did not live through his MW prime. No one could literally win a round off him or even land a shot on him in his MW prime. I would pick RJJ to win a UD against Triple G. It would be a close call because Triple G is clearly up there. I do not think Triple G would land on Roy I really do not.
For gods sake Roy wasn't roided when he fought at middleweight! What happens when you are on roids? You start gaining weight. So he most likely started using them when he was about to move up to HW. You guys are the most deluded ever. Roy's chin wasn't cracked at the time he fought at MW. Golovkin surely couldn't keep taking Roy's shots all night long like he's "allowed" other fighters to, or at least he would get a Pizzaface too bad to continue. People here really hype any decent current fighter so much it's crazy