I just started keeping roaches myself about 6 months back and am feeding off my colony now. I use sorting buckets with various sized holes and typically just pick out the non-moving roach carcasses after sorting. I have read though, that some keep a cleaning crew in their roach colony to dispose of the bodies... I want to say beetles of some kind (dermestid maybe). I read this on a bioactive group on FB, I'd suggest you ask on a bioactive forum / group and they should be able to tell you.