Who use dermestid beetles as clean up crew? The usual beetle for that matter is Alphitobius diaperinus (or any tenebrionid), maybe dermestid beetles don't eat oothecas?
I have several tenebrionids, A. diaperinus are in my dubia roach bin because those roaches keep the ootheca inside, but I can't put any tenebrionid with my red runners because they lay the ootheca and the larvae could eat that.