I played this MU vs Holy at EGE, a tournament he won, he gave me some interesting insight on the MU.
Firstly, D-air doesn't autocancel in short hops anymore, only in full jumps.
Neither Wario nor ROB like being in the ledge against each other. ROB can leave a gyro spinning by the edge and deny Wario options to come back onstage, while Wario has a bike that can be thrown and bite to cover most getup options. That said, ROB has a significantly easier time setting up his gyro trap, it's much easier for ROB to deploy the gyro in the right spot than for Wario to ditch the bike so it stays where he wants it. ROB can also just go under the stage and U-air Wario while he's throwing the bike up or attempting a chomp trap, just watch out for him shielding it cuz re-grabbing the ledge is going to result in Wario D-air spiking ROB, or worse he could just waft you and end you.
Wario is capable of eating all of ROB's projectiles as long as they correctly line up with his mouth. So if you hit his head, he won't eat it and take damage instead. Keep in mind too that eating a gyro recovers Wario 1% (measly) and charges Waft by 1 sec (dangerous). I wouldn't go as far as to say Gyros are useless against Wario, just be smart about how you toss them. If you expect Wario to Chomp, then don't throw it at him, glide-toss towards him by throwing it down and attack him instead. Chomp gets beaten by attacks, it's a command grab. Likewise, Chomp being a command grab means it beats shields: watch out if you shield on platforms or when Wario is landing near you. This is a general Wario thing to watch out for, no matter which character you play against him: always respect the bite, he can snatch you if he catches you shielding no matter where he's coming from.
Whenever ROB recovers low, it's an almost free waft for Wario because of the way ROB's hurtbox behaves when he's recovering / grabbing ledge, and also because of how low the Waft hitbox actually is (it's deceivingly lower than the gas cloud startup). Recovering can be a pain for Wario as well, despite his bike giving him options. You as ROB have a laser, gyros, F-air and U-air (if he's recovering high), all of which used together can stop Wario. He is unable to use the bike again if he's knocked off it offstage until he lands again.
ROB outranges Wario for sure. Wario may be faster than ROB in the air and in frame data, but that doesn't mean you can't space tilts and aerials against him. N-air is especially awesome against Wario because of the travelling hitbox around ROB and the explosion makes it hard for Wario to find a safe time to go in with how long it lasts. Wario's F-air can't deal with it's range, but it can catch ROB on startup.
You can stop Wario's onstage bike shenanigans with a laser from afar. It pierces through the bike and Wario will just fall off. Keep in mind the bike also loses its hitbox when you knock Wario off this way, I've seen other ROBs knock me off this way and shield the incoming bike when there's actually nothing to fear. The bike's hitbox is only active if Wario jumps off it.
If Wario is already close to you with the bike, it may be tempting to shield and then try shield-grabbing him, but this isn't a good idea if Wario knows what he's doing. Wario can do a wheelie to generate another hitbox or to a 180 to generate multiple hitboxes on the back wheel. The best thing to do is sit on your shield and D-smash as soon as you notice the bike go past you, you'll knock Wario off the bike and you'll also be hitting behind you. D-smash is one of ROB's fastest moves when being pressured (as I'm sure most of you are aware).
I'm sorry I don't know more about ROB's moves and how they interact with Wario, I've been doing this mu more with Fox lately. I hope this helped nonetheless, and I'll edit this if anything else comes to mind.
Holy is a real homie too, always shares advice with me after we play together. This man beat all of Ontario + Nakat last weekend at GOML and took it for Montreal. Best ROB in the world imo.