(1/20/2014)
Rob is definitely a unique character introduced in Project M and has a learning curve on how to deal with, even for Melee veterans. First of all, you should know to respect Rob's gimping abilities off stage. With his boosts, he can reach far and deep off stage. His aerials also get a slight power boost when he does them right out of his boosts. If he boost f-airs your shield perfectly, it is only -6 on block, giving him 2 frames to jab you before an oos up-b can hit him. His jab however, isn't that safe on block, so it becomes a game of chicken. Sometimes he'll f-air and then jab your response or he'll aerial then wait or even just aerial -> grab you if you decide to always respect his f-air. When facing a Rob on the ground that is in nuetral, be careful of how you space and time your projectiles. His reflector tackle (forward-b on the ground) is good at coming in on your boomerang and arrows and hitting you leading in to some stuff. Bombs are a little safer to throw out against this, but you can still get hit by the tackle itself. And don't forget he has that self-recharging laser. It has transcendent priority, so it will go through anything and it has some nice knockback too. If Rob can't follow up after knocking you off stage, he might try and read when you jump (or when you won't jump) and laser you so always be prepared to react.
So now that I've talked about some of the scary stuff Rob can do, let's bring up some of his weaknesses. First of all, his shield kind of sucks. It's pretty small for a big robot like him, so it often leaves his bottom or his forehead exposed to attacks. Using your projectiles (especially boomerang), you can whittle down his shield a lot then try to poke with d-smash, f-air, d-tilt, z-air, or even d-air! Rob likes to dash around in the air with his boosts to mix up his timings, but doing this leaves him very vulnerable to projectiles. He can f-air away the boomerang if he hits it with his robot "hands", but if you get his head or belly, he'll plop up perfectly to get combo'd. Alternatively, if you have the opportunity, you can throw a bomb which will also hit him easily in the air.
Edgeguarding Rob requires some practice and is difficult at first. Remember the way his boosters work. He gets 3 boosts in the air and doesn't get them back when he lands. That means, so long as you hit him and reset the situation off stage enough times, he will not come back. The object isn't to hit him far away (though it never hurts to do so), but to hit him after each boost attempt. I find the best tools for this are arrows, b-air, and aerial-up-b. If Rob is coming from a far, aim arrows at him. If Rob is coming from low, hit him with b-airs and up-bs that end with you grabbing the ledge, then go back into more b-airs. The trickiest angle is trying to stop him from coming high. Rob can mix up a lot from above by using his boosts and any of his aerials to change the timing of hitting him. From above, he can also drop his gyro to zone you out of the air, giving him a safe place to land. You can hit him with u-airs, f-airs, bombs and boomerangs here. F-airs are the most preferable because it will knock him back off stage or possibly KO him. U-airs are okay, better if they KO off the top, but otherwise, he is sent upwards and now has a good chance to make it back. I would say bombs and boomerangs are the worst options, but sometimes it is the projectiles or nothing. These two projectiles will send him back up in the air, but rarely will KO on their own, and Rob is so floaty that it is rare you will get a chance to combo off of them when he is that high in the air.
I wish I knew how to explain what to do when Rob starts juggling you from the stage towards the blast zone, but a lot goes on in a short time. This part is crucial to learn when it is best to try and jump out of it and recover high and when it is better to go low as possible. I would say learn to be very comfortable recovering very low vs Rob. The worst thing you can do is try to recover anywhere near ledge height. It's a sure way to get bopped.