one way that I've combatted the escapee in the cage scenario, is with that product advertised in the feeder classifieds, bug barrier, or a similar product... I would get a rubbermaid container, which was sturdy enough not to be tipped over by the animal, and would then line the inside rim with the bug stop. I would then place this rubbermaid(could be any size, as long as it's untippable) in the animal's cage, throw the roaches in, and presto!! no escapees... Plus, by being in a confined area, the roaches have nowhere to go, and the animals can easily pick them off at their own leisure..
AS for hissers, I never really liked them, for they were too big for my monitors...perhaps if I kept larger species they would have worked out... so when I did rear them, I would feed out nymphs, and keep all adults as breeders... because I keep smaller odatria, and prasinus complex animals, I began rearing smaller species, such as lobsters(my favorite-breed astronomically fast), discoids, suriname spotteds, and orange heads.. The latter three, get rather large, but not as large as hissers, and their bodies are a bit softer, which might be easier to injest... I don't think that the hard exoskeleton of a hisser would be hard for a monitor to digest, I just think for a smaller sized animal, it might be difficult to overpower, and fit down its throat...I would think monitors would have invinceable digestive juices, that can handle pretty much anything they come across...
Good luck with your roaches, and congrats on your lowered feeding bill!!!!hahahaha
take care,
bob