SouthWest does just Orlando, it seems. I believe they have two non-stops a day.
It doesn't seem that any of the airlines covered by Orbitz goes non-stop to Miami (or Ft Lauderdale) from Buffalo. AirTran will get you to FLL from Rochester NY, but I suspect that the Toronto to Miami route would be more convenient for you (unless you happen to be on the Niagara Peninsula); this is flown by both Air Canada and American, with the latter coming in with the better pricing from what I can see.
Good luck!