Roaches don't have shells and have very little chitin.. impaction is rarely caused by them if ever. I have never heard of someones animal getting impacted from one. They're a huge staple in a ton of animals diets, frogs included, People use them because they're much healthier than crickets and a lot easier to breed/raise, making them cheaper than worms. Grif said an adult "can constipate" a frog, not impact it. Impactions are much much worse and can kill, I have never heard of a roach ever killing a frog because it couldn't digest it.