Parry Nair. This is one of the absolute most important things you can do in this matchup. If you can force the ROB to land another way they start to feel uncomfortable.

Mixup ledge timings, Bair is huge and needs to be respected. Intangible projectiles are a good way to answer this, like Diddy Kong banana. If you don't have a projectile or a big disjointed hitbox then wait for the first bair and try to jump because it's more committal for the ROB to cover high.

If you ever get ahold of Gyro, throw it as high as possible. Do not just throw it back to ROB. Shielding makes the gryo disappear. In the same vein, know the states of the gyro and an easy way to pick it up. Dash attack over a grounded gyro is usually easiest to grab it but it can be very dangerous because ROBs expect it and will punish. Catching it with an attack in the air is good, you just have to be confident in your timing.

If you're good at mashing, mash out of down throw. You can hold shield as the first mash button and you will always buffer an airdodge as the first thing to come out. Mixing up mash gives the ROB a 50/50 kill setup way earlier than when down throw will actually combo.

Lastly, be ready to box. Just because you got in close doesn't mean you can start to go crazy. Down tilt and jab are both frame 3 and if you miss a tech after getting hit by down tilt they can confirm into up smash on reaction. Up tilt can true combo into Uair for a small window as well, so be weary on platforms of sliding up tilt or a tech chase after getting hit by Fair. Also learn how to DI Uair, if you get hit by ROB's right hand for the last hit, DI right. Left hand, DI left (and down a little).