Some thoughts on Roy vs. Marth
So me and my Bro played this game for a very Long time now, with him maining Marth (being a decent one) and me Lucina. After a short time playing Roy I decided to main him and play a bunch of games against my Bro and noticed some things:
1) Marth's outrange over Roy can be a thing
A good Marth switches between defensive Spacing and Offensive pressure with edgeguarding. Marth has good Struggles and Edgeguards to make it hard for Roy to get back on the Stage. Your only option is to recover really low, otherwise Marth will outrange you when trying get on Stage by throwing out Attacks, and even a dodge is not Safe when your opponent got a good read. Finally, he can jump into his Recovery with a Counter (what Roy can do as well, but Marth's UpB is faster than Roy's, 5F against 9F)
As his Range goes, he can be devistating for Roy in the air. NAir and Fair will outrange, and if they do, hit with the Tipper.
His Tilts will do the same as everything mentioned before, same goes for his Smashes.
So, how to deal with this? The best answere is Roy's mobility over Marth. Dancing around and not giving him space can work out very well. Grabing can interrupt his plays and set up combos pretty well
2) The Kill-Power
As we all know, Roy got no problem killing people: his utilt/ftilt, bair/dair, FSmash/USmash and NeutralB/UpB. He can kill with ease at around 60% at the Ledge.
However, a good Marth is using his Tipper consistently. This means allmost as much Kill-Power for Marth, killing people with his SideSmash at 60% (at the Ledge). UpSmash is a good Anti-Air Tool. Due to his range and the Tipper he can gimp people by far easier than Roy. But then again, Roy just got more Options.
3) The Tipper
As said before, due to his spacing, a good Marth will consistently hit with his Tipper when trying to go for a hit. At this Point Roy can't go with the Space-Game for two Reasons. First, he's going to get outtanged and being hit by a Tipper. Second, if he trys to space as well Roy will most likely hit Marth with the tip of his Sword which deals less damage. This IS a Double-Advantage for Marth: Roy deals less damage when he get's hit (which won't happen that much), but at the same time he deals more damage when Roy get's hit (which is more likely)
This is just my opinion and experience so far (sorry for any grammatical issues)