If Dariusz had Futch in his corner he would probably win, Futch worked out Jones weakness`s for the 1st Griffin fight and wasn`t in the corner for the second fight Roy might come out blasting like he did in the second Griffin bout then the tables will turn I believe.
Jones stops Dariusz, too big gap in speed/reflexes. Or at least wins wide decision - Michalczewski was very tough fighter and wouldn't give up. Roy would play with him like he did vs John Ruiz.
I'm assuming prime vs prime. As 168, I don't think anyone beats Roy except for Sam Langford. AT 175, he's a bit lower in skill set but still beats this guy (don't want to spell it out).
DM was legit. A very good fighter... but he'd have been outta his league against Roy. Roy by wide UD.
Disclaimer: I was a DM fan at the time. Wish that one would have happened. They beat the same fighters at 175 to a large part, Jones looked mostly better. Neither would have faced someone of the quality of opposition the other was. I think overall Jones was the better fighter by a bit. However, DM hat a decent defense, a good chin, the power to knock Jones out, could bring on the pressure and was always ready to take some to give some. I can see Jones doing his thing, cruising to an easy looking decision win but if DM manages to make it rough, drag him into a different kind of fight he will drown him. More likely Jones wins on points though.