I've been trying to get Studio One to do what Sonar does so easily. Anyway, as Zargg has already explained, just bounce or record EZDrummer to audio tracks, then process and automate those audio tracks any way you like. You can then freeze and mute the EZDrummer synth. If you need to come back to it, tweak something and bounce to an audio track again for whatever reason, it's still right there in your project.
Not sure if you're using multi-out from EZDrummer, but you can assign each EZDrummer mixer channel to it's own audio channel in SPlat. In that way you can process each kit piece, the room, and so on, individually. There are threads and tutorials on doing that.
Btw, for the longest time I didn't know that you could record the output of a synth like EZDrummer to an audio track.