When it comes to reheating prime rib, the worst mistake you can make is using conventional methods, such as a pan, oven, or microwave.
Steaming is the way to reheat prime rib properly. Start by cutting the remaining roast in slices and place them in a baking dish with a little liquid
Cover the pan with foil and bake at 250 degrees Fahrenheit for about ten minutes. The liquid will evaporate and turn into steam, gently reheating the meat.
You can also reheat the meat on the stove by wrapping a slice of prime rib in foil and placing it in a steamer basket over a covered pot of simmering water for five minutes.
If you use a microwave, fill a dish with liquid, but ditch the foil, which isn't safe to put in the microwave.