Hi Fallenleopard,
First of all, do you have the PS3 version or the Xbox360 of the drumkit? I know the xbox 360 version when connected to the wireless receiver is identified as a gaming controller. Therefore, you should be able to map the pads to the keyboard controls.
Check this out:
http://www.youtube.com/watch?v=pOfgJ5S_Az8But instead of using the guitar, use your drumkit.