I have watched many Phoenix games this season and my observation is that Roy has benefitted a lot from Parent carrying the puck and establishing puck control in the offensive zone, especially on the Powerplay. This is what I'd like to see from him more next season. Carry the puck, enter the O zone in control of the puck, establish the cycle game down low, move his feet.
Roy has had a tremendous season and is having terrific playoffs so far. He does need to prove that he can do more of the work leading to goals than he has this year though; become more of a play driver, in my very personal opinion. Obviously, Roy is a skilled player, but I find his points to come a lot from the same areas/same plays. It's one thing to do it when you're Ovechkin or Stamkos, it's another when you don't have that pedigree.
I can't speak for all the guys that you have mentioned. But MacKinnon was an absolute force out there when he had the puck. He skated with authority in possession of the puck and drove the play like few other junior players. This is essentially what I'm finding Roy is lacking and this is also what Parent is providing. Joshua Roy is a very good prospect that still needs another year in juniors. Let him take that locker room; be that undisputed leader; learn to drive the play night in, night out. 1 more year will do him wonders. Then he can join Laval for a year or 2; then I could see him becoming ready for the NHL.