I have thousands of these. I put traps in my roach feeder bins and catch 300-500 larvae at a time. Be aware they will crawl out of most enclosures with 1/8 inch holes in the lid. They will get into other enclosures. Kind of a pain...
Lesser Mealworms can be a part of an effective Cleaner Crew for Roach bins or Enclosures. They eat miniscule grains that roaches miss. I raise them and offer together with other species that eat flesh as well as vegetation and mold. An effective Clean-Up Crew will contain several species all that specialize in various specific jobs while being harmless to your roaches.