Usually I let mine sit out until they reach room temperature and then into hot water they go. Last time I feed I skipped the hot water step and I had a pretty successful feeding with 4 refusals, 2 because of shed, 1 because she prefers live and 1 because she lives to make my life miserable.
Out of 25 BPs that was a pretty successful feeding and I think I will just skip the hot water in the future. My super picky cinny who was only eating solid white live mice even took one of the f/t multicolored rat pups.
Edit: I feel like I should add, room temp in my apartment is like 75-80. I don't pay for heat so it's the cheaper way to go. >_>