My advice is play a different character.
If you really want to play ROB in doubles, I recommend partners with high mobility or the ability to capitalize off of laser very easily even if they happen to get hit by it (Yoshi, Wario, Sheik, Falcon and that lot). If you are stuck with something less desirable (big, huge characters are bad partners for ROB because he will accidentally hit them a lot), I recommend you be very restrained with your attacks. Focus on spacing and lightly punishing your opponents for trying to gang up on your partners. If they come after you, focus on defense and escape. Do not try to engage both directly often because you often hit your partner when they try to come in due to how large our most protective hitboxes are. ROB is not much of a killing machine in doubles. You want to facilitate for your partner mostly. Uthrow and dthrow are mitigated due to how slow the are, allowing for opponents to save each other from them often.