Do not fight Roy like you'd fight Marth or Lucina.
He is nothing like them.
You have to respect his strength, he can get up close and start smacking you around in the blink of an eye and his combo game is devastating.
You can't win with just muscle, either: you have to play judiciously and space him out.
The tough part is keeping him out at all, because he's so damn fast. His sword will make your life hell if he gets close to you, and Pit's toolkit is just not quick enough to push him back.
This is where grab comes in handy. Roy is fast and strong, but his moves are not safe on shield, which makes him grab-bait. This means you can soften him up and toss him over the edge, which is where the real fun begins.
Roy is great in the air when he's comfortably above the stage; when he's trying to get back, though, he's vulnerable. Pressure him with arrows and force him to either take the hit or airdodge, both of which will make it more difficult for him to make it back to terra firma. If you're very good at it, you can even force him to waste his jumps, which makes keeping him off-stage even easier.
Contrary to popular opinion, Roy does not have a terrible recovery. While the recovery itself isn't stellar, it can be angled vertically or horizontally, travels a good distance for his weight class and - this is the kicker - is invincible and can kill.
This means you do not challenge Roy when he's recovering. Pressure with arrows and even going deep can make it difficult for Roy, very difficult indeed, yet you must be very cautious of Blazer. It's Roy's secret weapon and he will use it to get you if you're not careful. Do recall that this applies to any stage of the match, not just off-stage, as it's a good recovery / OOS option and can royally screw you over if you're trying to challenge Roy, on-stage or off.
If he's edgeguarding us, then standard Marth / Lucina rules apply: he'll try to chase you off-stage with f-air or poke you with d-tilt, though there is the added hazard of Flare Blade to deal with. Flare Blade is incredibly easy to evade, so long as you don't try to challenge it. Roy will use this as a scare tactic rather than a real damage option, forcing you to either wait until it's worn out or approach from above, which is easy pickin's for Roy's solid anti-air options and punish game. You can try to challenge Flare Blade with a getup attack or rising u-air / retreating f-air, but do so with extreme caution. Remember that Flare Blade has no lag whatsoever, which means he can throw it out to cover the ledge and then immediately follow up to punish our approach. Get a feel for how Roy uses Flare Blade and then work to mix up your getup options.
Quick recap:
- Roy is faster than us and stronger than us, and he will pressure us as best he can
- Spacing works: f-tilt, f-air, d-air, b-air and d-tilt are your friend
- There's no point in trying to challenge Roy to a boxing match, you will get bodied for it
- Don't underestimate Roy's ability to recovery or his up-b's kill potential
- Flare Blade is a good edgeguarding tool - psychologically, if not physically
- Grab, grab, grab, grab and never stop dancing
Oh right, I entered an amateur tournament at a con today and came third. Very happy with that, and I got some very cool compliments on my Pit!