The piano roll in any sequencer/DAW just allows you to trigger some MIDI data such as notes, and other MIDI contollers. In order for you to program drums using the Piano Roll, you'll have to set the MIDI track where you're messing with the piano roll to output to some kind of sound source be it a plugin drum synth or sampler or some hardware sampler.
Once you've set up the routing, then you'll have to figure out what MIDI notes trigger what sounds. For example Kick drum might be on C2, snare on D2, etc.
Once you've figured that out, then it's just a matter of programming your pattern.