Ok, this is mostly SPECULATION as I don't fight ROB mains, but don't characters that space well and aren't forced to approach good ROB counters? ROB controls space pretty well and can just shoot ya if you try to set things up, so I'm not sure if a character like Link has much clear-cut advantages over him, but what about Shiek, Falco, and Wolf? They can all return fire pretty quickly and IMO beat ROB out with their projectiles. On top of that they can take advantage of his so-called 10/2 and 6 o'-clock blind spots when they approach. All three can either combo him into oblivion, juggle him silly, and kill him off the top.
Aren't those easy matchups?