I believe we were having a discussion in another thread in these boards about the playstyle differences between roy and marth. Things to remember:
1. Marth is good.
2. Roy is bad.
3. Learn to avoid Roy's bad ****.
In order to play Roy effectively, you need to accept he is bad and move on from there. He has very few good matchups, and of those, you will rarely see them in tournament play. Now that we've accepted the badness, we're going to examine it. First step: why is he bad? List: Lack of hitstun, spacing game is inherently worse than marth, seemingly random/dead hitboxes, and no aerial priority. Second Step: Bad matchups. Fox, Falco, Marth, peach, jiggs, ganon, shiek, samus. Wait, what?! Yep, that's the whole top tier plus most of the high tier. Of those, I find shiek, jiggs, and peach the worst. Falco is really hard until you learn to powershield pew pew.
So he's bad, how do I play him?
Well, that comes with plenty of trial and error. But what you need to know is that fsmash is your best friend. Side B is your most useful attack in your arsenal, often putting people in places where they can be fsmashed. Side B(DED) has so many uses, its ridiculous. Lastly, the combo move: dtilt. This move puts people into fsmash position, so make sure you have plenty of WD to dtilt skill. Am I forgetting something??? Hmm... Oh right. GRAB. If you're used to whoring it up with marth's magnetic homograb, then you're not going to miss much. Roy's grab (as far as I can tell) is almost as good as marth's with some small directional changes and slightly less range. Other useful moves that aren't as good as those other ones:
neutral B (flare blade), dair, uair, fair and nair?
Good stages?
Your preference really, I <3 FoD and FD. I </3 battlefield. Dreamland is my most neutral stage. With YS coming in at a very small positive for me. I hear a lot of Roy players really like FoD for the sweetspot fsmashes on platforms.
What do I do if I play shiek/peach/jiggs/*disliked matchup*?
Get another main. You will not beat most competent players that know how to beat roy. If you're really stubborn, go get *****, and get *****, and get ***** again. You'll know the matchup after a while of that (I know the ganon matchup really well). Orrrrrrrrrrr.... you pick up another character with good matchups vs your bad ones. For example, I also play fox and Zelda. Fox deals with the awful shiek matchup that both Zelda and Roy offer. While Zelda takes care of most of the other bad floaty matchups, such as Peach and Samus and Metaknight.
Closing notes:
CC>Roy
Use your sideB to fix anything you're having problems with.
Roy combos are sexy.
Tires don exits
Fire>>>>>>>>Everything