Traditional methods of reheating roasted chicken at medium oven temperatures often wind up re-cooking it, which dries it out, and the skin rarely crisps back up properly. However, flashing, a method used in some professional kitchens, reheats food at high temperatures for about two to 10 minutes. This method reheats the chicken quickly without it starting to cook again, which helps keep it moist. The temperature is also high enough to crisp the skin to perfection. Flashing only works for meat that is small enough to quickly reheat, so you may need to break down your chicken roast first.
Take your cold roast chicken out of the refrigerator about 30 minutes before you plan to reheat so it can come to room temperature. Preheat your oven to between 450 and 475 degrees Fahrenheit.
Cut up your cold roast chicken into individual portions if it is not already broken down. Using a chef's knife, cut off the legs and the wings at the joints. With the breast facing up, position your knife just above the backbone and slide your knife through to remove the breast, and then divide it into equal-sized quarters.
Spread the chicken pieces in a single layer on a baking tray. Brush the chicken parts lightly with softened butter, which will help crisp the skin and keep the chicken moist. You can also spray the chicken lightly with cooking spray.
Cover the tray loosely with aluminum foil and place in the oven to reheat for about five minutes. Open the oven and remove the foil to allow the skin to crisp and reheat for another five minutes or until the chicken has reached an internal temperature of 165 Fahrenheit. Use a meat thermometer in the thickest part of each chicken piece to determine the proper temperature.