Hahahaha, trust me. I know EXACTLY how this feels, LOL.
I still get beat by this occasionally.
Your first step here is predicting the rolls and predicting their directions. It might seem patternless and random, but this sort of playstyle has its own rhyme and reason. Once you can predict rolls, you can act accordingly. Dealing with the forward smash can be tough because not many characters can just "beat it." You'll have to space yourself pretty well and even run away if you have to. If you're far enough away to space your own forward smash (doesn't sound like it, though), then try to get him in the lag of his own, but watch out. Falco's has longer reach then he lets on and it's quick to recover from as well. If you're super close (like, SUPER CLOSE) when he starts it, shield as hard as you can and as soon as you feel him hit you, let your shield down or shieldgrab. If you let your shield down early, you can retaliate with tilt spam. If you grab, throw to combo to KO.
Now, how to apply this. Here's the fun part (especially if they're rolling behind/around you). You stand there and face the direction in which they're going to roll. Preferably before they do it. Just to add that lil touch of "LOL i see wut u did there" to the game. You can choose to do nothing if you really want. That kinda drops the hint that roll spam might not be the other player's best option. You can also choose to exact your revenge through down smash (this also stops roll spam pretty quick), forward tilt, and charged forward smash. Of course, there are many other things you can do (like DJC neutral air to death combo), but these let the opponent know much quicker that you've caught onto the crux of his/her game.
I know it sounds silly, but for every roll the player spams, spam your own patience and foresight. Beat forward smash spam with intelligent (a.k.a. "justifiable" a.k.a. "just-as-bad") tilt/smash spam on the roll/smash lag.
Of course, the first time I encountered this after I started playing Yoshi seriously, I just picked Peach and...well...yeah. I used to lose my cool against this sort of stuff.
or cc dsmash spam.
