Always have Tinkerbell out. Not only is she good to have because she's pretty much a Regen spell mixed with a one time Auto-Life, but also because summons disable all triangle button commands, including the "Release" command during the roulette, lowering the amount of commands you have to shuffle through to three.
One you get his purple lifebar down, cast a Cure spell on yourself after every attack he does. If you have MP Rage(s) equipped, you'll more than likely get that MP back really soon anyway, but you're moreso doing it because if you do it (and have Leaf Bracer), even if he uses the roulette attack, it won't hit you, and thus, the attack won't activate.
You can also just bring a ton of elixirs and spam Strike Raid once you get to that point too, since Strike Raid has invincibility frames that protect you from anything during the attack.
Once you get him down to his final pattern (This pattern starts with his desperation attack where he encases himself in a sphere of light and goes all laser light show on you), it's actually a bit easier to tell when he'll use the attack, making it easier for you to nullify it with Cure/Leaf Bracer. He'll start shooting red laser shots that'll track you. As soon as he's fired all of them, use Cure. His AI tends to use the attack immediately after if you happen to be moving towards him during that phase, so that's something to take advantage of. If you have a surplus of Ethers and Mega Ethers, give a bunch to Goofy and set his AI to use them on Sora. Those'll be invaluable.