I used Sony Vegas 8. I didn't really know Sony Vegas back then so I'm really eager to see how I do now that I've messed with the editing software a bit.
Anyway…for ROBs, since lots of ROBs attacks can't be aimed diagonally, the best approach would be from the air. Also, use platforms to your advantage to get ROB into the air and try to juggle him as his aerials are slow. He is also surprisingly light over the top so if you can get a good Up Smash in, theres a good chance of a kill. As for G&W, since most of Mario’s aerials are faster then G&W’s its best to meet him in the air as Mario has bad range on the ground.
Pretty much, use your Mario’s aerial superiority.