How are you offering the frozen thawed? Probably one of the more common mistakes when trying to feed f/t to a shy feeder is to dangle it above them. Generally speaking, death comes from above - not food. Use some long handled hemostats, tweezers or whatever you have to grasp the thawed and warmed rodent by the scruff of the neck and proceed to zombie dance. Zombie dancing is trying to make the rodent act like a living one. Watch your snake feed on a live and try to mimic that. If it usually waits until the rodent noses his face you could give that a shot after dragging it around a bit. See if he tends to hit the rodent before it gets too close, from a hide, when it's facing him or facing away, etc. You are the puppeteer and your rat is the marionette - proceed.