It's very strange if you get sound with the step sequencer but not in the piano roll, since it's basically the same thing in different costumes.. (I know it's a bit more than that, but in this case it shouldn't matter)
The only thing that comes to mind at once is that you maybe had superior drummer's audio track selected when opening the piano roll view. To get sound you need to open it when superior's MIDI-track is selected. I don't know if you created a seperate MIDI/Audio-track or an instrument track or if you know the difference of these different kinds of track types though
I think it would be easier for us to understand what might be wrong if you could explain exactly how you do, step by step. :) The more you explain the better understanding we'll get of your knowledge about these things as well.