ROB is pretty significantly in MK's favor, if you powershield his projectiles he can't really stop you from getting in on him, air camping works very well against him, and he's surprisingly easy to edge guard considering how good his recovery would normally be considered, but his ability to stall for time in the air simply isn't as useful vs MK as it is against other characters, and he's wide open while he's doing it. he also has a ridiculous blind spot below him, guess where MK likes people to be : D if you get a good lead it's really hard for ROB to do much because MK's defense is so good, most projectiles will just be shielded, and aside from fully charged gyro none of them are likely to kill you anyway if you do miss a shield.
a lot of ROBs attacks have deceptive properties like nair punishes pre-emptive spot dodging because its slow or bair is an automatic spacing trap, nair also has very low landing lag, generally being cautious around these things helps. other things to be aware of like you can SDI out of his dsmash to avoid the KB hit. nair, fsmash, and bair tend to be the main killers, uthrow also kills at very high %, fsmash is frequently stale because it's one of ROBs main anti-tornado moves(this should tell you something about how good tornado is in this MU), but may kill on reset. don't get hit by uair, it does a lot of damage.
stages...I'd go with standard MK stages(SV, delfino, RC etc.) with the exception that I actually wouldn't recommend BF, ROB has great platform pressure too and I think it aids his camping a bit, it's still a good stage it just wouldn't be my #1 choice. ban japes or FD? I'd probably go for japes just because I hate that stage in general
you can take the gryo instead of shielding it sometimes, without it ROBs camping is a lot more tame as his laser is rather slow to recharge and you can still tornado/fly around/block or whatever, MK's glide toss is also pretty great, glide toss gyro > dsmash is 21% and works at low %, at higher percent you can throw it down if he's open for the kill...glide toss > tornado is something I just thought of that amuses me