IMO, i wouldn't leave the rodent there for a long time but if its how he eats, then its how he eats...
your temps,humidity sounds fine, do you have any pictures of the his cage?
but as long as the ball is eating it should be Ok, when my ball doesn't strike i just leave the rodent in their for about 10 minutes in pitch black... if he hasn't had it then i just throw it away.