Yamaha DTXpress/DTXplorer/DTXtreme

I have had my Yamaha DTXpress II kit for 2 months. I was just 
wondering that if in the future if I wanted a Roland PD-80 pad or PD-
120 snare pad, would it work? Are they compatible. The same goes for 
the V-Cymbals.
Has any one got a DTXpress II with additional Roland pads.

Thanks 
Tim