I'm unsure if woodlice can carry parasites that are transmittable to frogs (I have a vague recollection that the answer is no, they don't). I would tend to err on the side of caution though and not use the ones found in your house to feed the frogs. You could culture them yourself though as an occasional treat. For those of us keeping tropical frogs, we often stock terrariums with tropical woodlice (they are smaller and reproduce quickly).