Culturing feeders you're bound to get grain mites. If you want to check out any dart frog sites you'll quickly see that. You could place your colony on mite paper, other than that, just whenever their population booms clean your roach colony. They'll probably come back, but you can at least control their numbers.

I actually microwaved my most recent batch of roach food and then sealed it in an airtight container. Although I wouldn't recommend that.