Roy's in his D+3 season and has 7 points in 17 games (.41 PPG) this year. He's starting to take a foothold on an NHL roster spot, and we can see clear flashes of skill.
Toffoli, who is similar in some ways as a player and one I'd also describe as complementary, didn't cement a spot in the NHL until his D+4 season where he scored 29 points in 62 games (.47 PPG). His game continued to grow from there, and he's at a career .64 PPG which is certainly a top 6 production level.
I think Roy is on a trajectory to be a decent second line player, but more as a complementary one like Toffoli. I'd like to see him play with a real play driver so his talents can be used more effectively. Maybe we'll see that with Dach next year.