Roy is a rushdown/bait-and-punish character that plays a lot like a ground-favoring Captain Falcon. His great overall speed gives him great combo potential, allows him to get the inner sweetspots on his opponents, and gifts him a severely underrated offstage game. However, the nature of his attacks make him a high-risk character whose defensive game is subpar, and his recovery is...alright, but not fantastic, as horizontal recoveries are gimped easily when it comes to this character.
I guess the main thing I have to say about Roy is that you can't be afraid. Don't try to space, don't play defensive - just go at them. Those sweet spotted attacks can kill surprisingly early. It's also important to mix up your movements so that you can bait the opponent into missing a Dash Attack or something and then promptly destroying them with an F-Tilt combo or F-Smash.
Also, I don't like D-throw into Up-B as cool as it seems. You get good damage, but lighter opponents can DI out of it easily and Roy gets a pseudo-chaingrab against some of the others. 23 damage might be nice, but you're usually selling yourself short on Roy's great combo potential - your best bet is going for an aerial depending on the direction your throw sends them, then try to string a few more hits off that.