(Tried to post this last night, but smashboards was being lame >.< )
These nice walls o' text are assuming that you know how to shield grab/shuffle/wavedash proficiently. If you don't, learn those first. Even if you do, practice shuffling alot, doing shuffles as quickly as you can, roy can move faster than most people think. Running off platform -> fast falled fair is nice and fast.
Falco: A pain in the *** match up. His lazers and pillaring should make it so its super hard to hit him, but when you do, you can seriously put the hurt on him. Spam dtilt; it lead to an easy forward smash, and then you just need a flare blade/counter edgeguard to finish the stock off. Upthrow -> fsmash works wonders, and at higher percent you can fthrow -> tech chase fsmash for the kill. You can duck under his lazers (unless they SHL them super low), so wavedash backwards -> dtilt is super nice, specially with the whole fsmash thing on top of it. Running attack has a nice quick burst of range and pulls you low, so it can hit falco out of a SHL at times, just be extremely careful trying it. You really want to sweetspot the ledge on recovery, unless you want to eat a spike and dump your stock.
Link: This punk has a bunch of projectiles, so most of the match will be you approaching him. You can fair right through his boomerang, just watch out for the bombs. Coming in with fair -> dtilt is really safe; even if he blocks, hes too slow to shield grab you after the dtilt, unless you just sit there and do nothing. Link is a good weight for dtilt -> aerial combos, so get those babies in and put the hurt on him. Hes also a good weight for dthrow -> fsmash. If they try to sweetspot upB the ledge when recovering, short hop and do a flare blade; the hop will make his swings miss, and the arch of the flare blade in the air will still hit him, providing you time it right. Watch out for his grabs, they hurt; at low % you'll be eating a dthrow ->uptilt/upsmash -> various aerial, and at higher pecents they'll dthrow-> upB (make sure you DI towards the center of the stage, and [smash]DI the upB hit, and you should still be fine).
Luigi: His wavedashing puts you at the disadvantage for ground speed, and getting hit by luigi hurts. Dtilt alot to keep him a safe distance away, and after dtilting just throw lots of little taps at him, making sure not to get in n/d/fair range. Your throws are practically useless in this match-up, he can jump out of dthrow -> fsmash even if he DIs it horribly. Maybe its just me, but charging flare blade at the edge doesn't seem to work. Instead, I usually dtilt -> full jump flare blade. It doesn't have as much knock back as a super charged B, but it racks up damage and is easier to hit with. Do not get grabbed; luigis dthrow will get you *****. Dsmash is a nice finisher if you rack him up to 100%+ and can't seem to get that fsmash/edgeguard in (just don't miss, wind down lag sucks).
Samus: Watch out for crouch cancelling; if she starts crouch cancelling alot, start doing more dtilt/grabs. With her rediculous recovery, you won't be killing her untill you get her to a high percent. Dtilt works wonders as always; as soon as you get her in the air, keep her above you with shuffle uairs and fairs and just rack on as much damage as you can. Watch out for he downsmash, it really just screws up your momentum and puts you in a bad position, not to mention racking up assloads of damage. Fair beats her missles, so don't be afraid to approach, just don't be stupid about it. Again, dsmash kills at high percents.
Lol, i totally didn't expect to end up typing this much out.
Any questions?