I've been feeding my roach colony exclusively veges and fruit for years and it is thriving. They get the leftover salads as well as kitchen scraps (dragon friendly food, no onions etc) and sometimes a treat of orange slices, some bread, or a banana. They LOVE squash almost as much as Darwin does so there is always plenty around. I haven't seen ill effects from this diet and at last check, Darwins UA level was in the normal range. Granted he only eats bugs once a week or so. I know it's a small sample size but perhaps the issue is more with what the roaches are being fed rather than using them regularly as bug meals.