In Buffalo, Roy spent his best years with Vanek on his wing. The last year here where he didn't produce he spent most of his time on the second line while Vanek and Pominville played together on the 1st line with a rotating wheel at center. Naturally when this happened Pominville jumped back to a point per game player while Roy struggled.
He could fit as a first line center with the right pairing, you'd Ideally want a scorer on one wing and big bodied power forward on the other. I wouldn't want him in a place where he doesn't have legit top 6 wingers to work with though.
I can only speak of his time with buffalo, but he was always passable on the draw and decent at getting back in his own end. Also got lots of time in every situation and got a lot of PK time. You might be comfortable at him at 3.5 but he'll never sign for that little. Someone will give him $4.55-5 mil over 3-4 years with how little is left at center.