Wow so Roy is...wow :/
Just got done playing with him, and I'd say his biggest weakness (compared to Marth) is not being able to chase offstage and not being able to kill in the air.
His ground game more than makes up for it. Fsmash, Upsmash, and super armor grounded up B are all great at sealing stocks and not hard at all compared to...Marth's tipper fsmash, tipper upsmash, and up b. I don't get why they made Roy so strong, logic should tell you it's way easier to hit with the entire middle of a blade and not the tip, so don't make the two sweetspots comparable in knockback/damage that's a slap in the face to Marth, and does lucina have anything that's stronger then Roy's sweetspot anything? Maybe bair, maybe upsmash, maaaaybe dancing blade, and if anything else probably not by much.
He's heavier too, which can be good and bad but makes him amazing at crossups and getting from point A to point B. He can FH fair and crossing landing upair, or my personal favorite FH fair and cross dancing blade, something Marth technically can do only he's floating the whole time so he spends a year and a day doing it and will get punished before he even lands. SH empty hops will BnB due to just how fast Roy falls and his run speed and grab reward. His jab is great vs speedy characters/to stuff moves/keep opponent honest, something Marth desperately needs in CQC situations, another fast button to press besides dtilt (which he kind of got this patch, have yet to use him against someone to see just how much better jab is).
Marth still zones/keeps out way better then Roy can, but Roy definitely has the tools to go in. Having a reliable kill moves feels so so so good. I wish the world was perfect and we could have perfect tipper spacing all the time, but we can't. Having a reliable kill move is so so so good, cannot emphasize that enough. No more being unable to kill the opponent because they're not at the right range. If they're in front of you and not shielding they are D E A D.
If Roy had Marth's shieldbreaker as well that would be insane.
Definitely picking up Roy. Will still use Marth in mu where range is key (don't see myself using Roy vs Mario, I want to keep that little bugger out) or where gimping/offstage game is important (falcon, link, i.e poor recovery people