Preparation:

Preheat the Oven: Preheat your oven to a low temperature, around 275°F (135°C). Low heat is crucial to gently warm the roast without losing moisture.

Bring to Room Temperature: Take the rib roast out of the packaging and let it sit at room temperature for about 30 minutes. This helps it reheat evenly.

Prepare the Roast: Place the rib roast in an oven-safe dish or roasting pan. If the roast is sliced, arrange the slices in a single layer for even heating.

Add Moisture: If you have some, add a few tablespoons of beef broth or water to the bottom of the dish. This will create steam during the reheating process, helping to keep the meat moist.

Cover Tightly with Foil: Cover the dish tightly with aluminum foil. This helps to trap steam and prevents the roast from drying out.

Reheat Slowly: Place the roast in the preheated oven. The amount of time needed to reheat will depend on the size of the roast. A whole rib roast might take around 1-1.5 hours, while individual slices may only take about 30 minutes.

Check for Doneness: If you have a meat thermometer, check the internal temperature of the roast. It should reach around 135°F (57°C) for medium-rare. Adjust the time for your desired level of doneness.

Rest Before Serving: After reheating, let the roast rest for about 10 minutes before serving. This allows the juices to redistribute, ensuring the meat is moist and flavorful.

Note: Avoid using a microwave for reheating, as it can cause the meat to dry out and become tough. The slow and low method in the oven is the best way to retain the moisture and tenderness of your boneless rib roast.