I'm styling this critique in the same manner I did on Bloshi's topic. I might sound a little harsh and nitpicky but I'm looking primarily for the faults and seeing how you can fix them. Here we go... starting with the last 3.:
Match 1: I can see right now that you're running into more of his fsmashes that you really need to. You should really stop being so reckless.
Also, following/getting behind him with rolling generally isn't a great idea, especially with the speed of Yoshi's roll.
Though you did make good use of the openings once you got that first hit in.
3:03 - if Roy's that far you really don't need to spike.
3:58 - Tap the analog stick left/right, then air dodge if you're in that situation again. Remember to aim upward so you can have a better shot at catching the ledge
Match 2a: You did more of the same mistakes from earlier(rolling to position yourself and running into his fsmash)... though that was a good start to end his first stock so quickly.
You're being too defensive at times though. You're lucky he's not grabbing you, because turtling like that usually promotes grabbing.
Remember not to rely too much on rolling behind your opponent, It might work the first few times, but honestly it shouldn't be working this much against a competent opponent.
Match 2b: 3:48 good use of jab to edgeguard. Much more effecient than that overkill spike in that previous match.
Match 2c: 5:11... you want to watch yourself around up+bs and other moves with a set/high amount of knockback. That can happen often with those moves.
6:21 - I mentioned this on Bloshi's topic, but generally you want to focus on getting back on the stage with Yoshi when getting back, not landing an extra hit. As I see it, there are some situations where you'll have to try and land a hit to prevent yourself from being hit, but that wasn't one.
I can see those two mistakes I mentioned on the first match are consistent in all three(two, actually) of these games played. I don't think I'll need to watch the last one to find if anything dractic's changed, but let's find out.
Match 3: Your friend whiffed several fsmashes at several parts(first instance I see is :24, though :33 would count too) but you didn't capitalize on the opening at times... something to keep in mind.
1:07 - good read on his roll.
1:48 - always remember to jump AWAY from Battlefield, not toward it.
All right, so I'm seeing some consistent problems that you want to try to fix:
-You roll too much in an attempt to position yourself. Jump move, and do some more DJC sex kicks, especially since your friend is fsmash happy.
-Those grabs were good but I don't think the forward/back throw were good choices(not just for the lack of combo chance following it but for the pitiful knockback they have). I would think down/up would work better followed by either uair or nair - depending on percent, of course.
-More DJC in general. It's a good trick to utilize especially against players like that. Use it as an extra method of floatiness to throw off their timing and throw an attack out too early to leave themselves open.
-In fact, your positioning needs work too. If you want to try rushing him like that, either fake him out with a wavedash backward when you run closer to him(you didn't seem to have much problems with wavedashing when you wanted) or dash cancel into shield.
Oops, nearly forgot. I would think Hugglebunny needs some advice too(even though it's not the Roy boards).
Now even though I main Yoshi/Marth, I know a few things on Roy and I'll point out some of the consistent problems you had with Roy like I did with burntsocks:
-Stop spamming fsmash. Roy has other options available if the guy's near him. Plus, doing it at low percent usually won't confirm the kill. Other options include: dtilt(make sure to crouch cancel), grabbing
-Speaking of dtilt, it pops the opponent upward. This, just like Yoshi dthrow/uthrow can help set up for combos. I would think Roy's nair would work just fine for this, and it does some good knockback, but it's up to you to decide how it works.
-GRAB. If you want to use fsmash, Roy's grabs can help set this up for you. Mix up dthrow and fthrow to use against him - if he messes up his DI or doesn't tech out of it, there's your opening. Remember to shieldgrab his approaches as well.
-Forward+B works for messing around with him, and it works for recovery(I didn't notice you use it much). Remember to string the combo together - I find it works better if you tap B after the last swing's finished(don't wait too long otherwise the move will end).
-You should really only use the up+b as a last minute desperation "get out of my face" attack. Don't spam it so much - if blocked or whiffed, he can easily take advantage of it.
-You also should be more defensive. You're being hit way too many times when you could have just defended the approach and taken advantage of the possible opening.
, just jokin
Going on offence at better times might be a wise move.