Roguelikes are generally RPGs, and there's plenty of them. See RogueBasin.

It sounds like it fits closer into the mold of Diablo 2 or 3 though, since as far as I can tell you're talking about an essentially real time RPG with procedurally generated worlds. That being said, that's not exactly a bad premise, but it might not be particularly competitive either. Though don't get too tied into whether or not people have done things like it before if you're just doing it for fun and as a hobby, you'll definitely get more out of a project by doing it rather than scrapping it because it's been done before.