I agree with clear. Insects really are not as susceptible to inbreeding as more complex animals are. It think this stems from a simple genetic code and a simpler developmental cycle while gestating. I wonder if roaches from other colonies would even get along?
When I first got into breeding many moons ago I thought it was very important to have a very diverse collection from many different breeders. I ordered roaches from at least 10 different individuals, including the large breeders. I never had a problem with introducing the roaches to each other. The only problem I discovered was that from one of the individuals I bought from had mites, and another had some weird beetles inside that soon almost took over the colony.
I get decay flies aka corpse flies (they may even be fruit flies for all I know) in my bins if I'm not careful. I usually keep fly strips on the lid to try to attract and trap any adults before they can lay eggs. The substrate that builds up on the bottom of the bin is perfect for these decomposing flies, and really they are harmless, however since I like to keep my bin inside the house when it gets cold the flies get out and are a nuisance in my home.