Well Roy has basically the same strength of moves as marth (many are stronger), only the sweetspot is in the middle of the sword not the tip. Some of roy's moves are slightly slower, though. You mention that marth can float in the air and delay his uair, but roy has the ability to shffl uairs much faster than marth does.
Platform camping does pose a bit of a problem, but I really don't like where this discussion is going. If I say that Roy can do X to stop Y, you will simply say how trashy it is or that it doesn't work or whatever, and nothing will get accomplished. Discussions such as these can only happen when two people are playing said match-up with each other.
Yes, Roy has weaknesses, but he also has strengths a lot of low tiers only wished they had. His ground game is amazing, he has an excellent SHFFL, his dash dance and grab are among the best in the game, he can use most of marth's edgeguard methods, his wavedash is quick and long and he has plenty of disjointed hitboxes.
Roy has some really ****ty match-ups with characters that can't be edgeguarded (puff/peach), but he probably has the best match-ups with spacies outside of the top 10. He does better than ganondorf or link, i'll tell you that much.
tl;dr, Roy is much better than kirby, pichu, and the like.
