Hmm, the second two videos you posted don't seem credible. The second one in particular seems to have misinformation, for example it lists super armor on Roy's recovery as a pro...but Roy doesn't have super armor on his up+b when he's recovering, only when he's grounded. Also claims Roy has the best punish game because he has a fast fsmash that kills early. :-/ Not to mention the creation date on both of those videos is super old. The first video, Art of Roy, is good, though.
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I'm not sure how much you've used Roy if you're listing dash attack as his amazing move, but I'll talk a bit on this subject. If you are a PM Roy main, the first thing you'll notice is that Smash 4 Roy's dtilt has different knockback, and isn't the combo tool that PM Roy's dtilt is. You can frame trap with S4 Roy's dtilt and get follow-ups based on that, but they are not guaranteed. Roy can combo out of his throws at early percents, and can use his sour spots, especially sour spot aerials and nair 1, though also sour ftilt, dtilt, and jab at later percents to set up kills. The reason why I raise my eyebrow on dash attack is because in tech chase scenarios, dash attack is the misinput because I didn't execute my foxtrot dash cancelled fsmash properly (kills muuch sooner lol). You can also tech chase with up+b and upsmash. This is one of the best ways to end stocks with Roy, so this is what you should be working on if you play him in this game.
On the other side of the coin, the thing you'll have to learn your way around is how to space with Roy. Everyone knows about Roy's high air speed but low air acceleration, but few people talk about what that really means. It means that Roy can move fast in any direction he chooses when he jumps, but once you commit to a direction, you have to use a resource (double jump) to course correct because he cannot weave very well while in the air. I made
this spreadsheet a while ago to show how you can control how far you travel based on how you execute your jump. Using this knowledge, you can actually execute proper retreating aerials, and cover huge amounts of space...but you gotta practice it, and it's different than for most other characters.
The other thing you'll have to learn as Roy is how to manage your disadvantage state. Roy eats a lot of combos, and you'll have to manage your resources (double jump) carefully, or you'll end up getting gimped. Knowing when you can escape is very important, so you don't end up getting your double jump sniped (which'll pretty much guarantee you'll eat double the amount of damage you would've otherwise). Remember Roy's up+b has better hitboxes in front than above, so using a diagonal recovery is generally better so you can have those protective hitboxes.
*yawn* ended up typing more than I expected lol. But yeah, this is some of the stuff you'll need to think about when using Roy in S4.
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since he gets the most out of being up and close.
This is misleading. Roy uses the full length of his sword same as any sword character. Sours lead into tech chases and can set up kills, not to mention they're less commital than sweets. Roy is about controlled pressure, knowing how and when to get in and get big damage, while also knowing when to space aerials and stuff approaches.