I've been trying out a lot of stuff with roy. Most of my friends only play heavies, so that's what I know.
Against DDD at 0, I can get fthrowx2>utiltx3>nair/bair/neutral b (but I don't think he's that great at DI). I love finishing up combos with nair. It's so good. I'm not the best at spacing atm, so this move is really helpful for me.
Other heavies, I can get fthrow>ftilt (anything else and they can tech before a regrab or w/e). Then follow up with a fair or dtilt etc.
I love ftilt sooo much. I don't think anyone has mentioned this yet, but I'm pretty sure that ftilt when timed right will ALWAYS beat mk glide attack. Much better than just sitting in shield. Fsmash and neutral b aren't good options against glide attack, but I think that ftilt is the answer. Can someone with experience with my mk players confirm this? I think ftilt will also beat tornado, but I'm not sure. Tornado is pretty bad now anyway, so I guess it doesn't matter.
So I get bored waiting onstage for my opponent to recover a lot of the time. It's difficult to go offstage and not sd with roy, though. He's just got a ton of cooldown lag from his moves, like fair, nair, bair, dair (ok I just listed all his aerials lol). He's such a fast faller that you can't recover. HOWEVER, I found that neutral b is actually great for offstage! It's got pretty low cooldown compared to the others. It's super strong even when uncharged, has huge hitbox, and you can b-reverse it if you need to. Sometimes I just like to troll a bit; fullhop>dj offstage so it looks like you're going after them way out there, but then just charge b for a while going down until you have to recover. Dem mindgames, man. I also like finishing regular strings with neutral b too. It's an awesome move.
I think I heard someone say that fair is safe on shield when you l-cancel, so either I'm really bad at l-canceling, or this isn't true. I just always get shieldgrabbed. Does anyone know how much hitstun there is for fair, and does it differ for different parts of the sword? Someone above suggested nair on shield; I haven't tried that yet but it seems good. Does nair have a longer range than fair?