Hi Marie, they are cleaner bugs just to help clean up the poop. They wont hurt but I recommend not feeding them. They are more of a P.I.T.A then anything.
The rabbit feed has a lot of by products the roaches don't need and cant digest. Depends on how much was used is probably why they where going after the greens to try to flush the chow out. Also did you notice any of the adults with any wing damage or look like they shriveled up? When they died...