Judging by the trailer, Flare Blade retains its overhead swinging animation from Melee, and Roy's F-Smash seems to be substantially different from Marth's, as well. Also, I don't think Roy's Over-B has been confirmed to be Double-Edge Dance yet, so that could be a new move, too.
Also, I'd like Roy to have a few differences from Marth and Lucina, too. I don't necessarily require it, and I certainly won't be upset if it doesn't happen, but I'd still appreciate some things to set Roy apart from his originals.
In other news, according to RandomTBush, the person responsible for all of this, Roy and Ryu are fully complete and ready to go. It's only a matter of time before we get our hands on them!