Room Temperature To cook evenly, the roast must not be cold let it stand at room temperature, loosely covered, for about 2 to 4 hours. This time can vary depending on how big or small your roast is. I can not give you an exact time on this. If you do not let the roast come to room temperature, if will take longer to cook your roast, your roast wont cook evenly, and you will end up with well done slices on the end and raw meat in the center. Use your best judgment on room temperature times Do NOT salt the outside of your prime rib roast, as salt draws out moisture from the meat while cooking. You can use other seasonings if desired, but I find it is not necessary. I know that some people do salt their prime rib roast before cooking, but trust me and do no salt the result will be a juicy, delicious roast to serve your family and guests Roasting Pan Place the roast, ribs down or fat side up, in a heavy stainless steel Roasting Pan or other metal roasting pan. Select a roasting pan that has sides at least 3 inches deep. I do not recommend using nonstick pans, as these pans yield fewer of the cooked on bits that make the tasty au jus juice or gravy. The rib bones are a natural rack you will not need a metal one. Cooking Temperatures Sear the rib roast for 1. F., then turn the oven to the lower temperature 3. F. for the rest of the cooking time. Every 12 hour, baste the cut ends of the roast with the fat accumulated in the roasting pan. Do Not Cover the roast. You will want to estimate about 1. See charts to make it easy to determine Prime Rib Roast Cooking Times. About 4. 5 minutes before the estimated end of the roasting bake time, begin checking the internal temperature use a good instant read digital meat thermometer. Play it safe and start checking early, as you do not want anything to go wrong. This is even more important if you are adjusting for High Altitude Baking. If you ignore every other bit of advice I have given, please pay attention to this For a perfectly cooked rib roast, invest in a good meat thermometer. Internal temperature, not time, is the best test for doneness and you do not want to blow this mealThis is the type of cooking and meat thermometer that I prefer and use in my cooking. I get many readers asking what cookingmeat thermometer that I prefer and use in my cooking and baking. I, personally, use the Thermapen Thermometer shown in the photo on the right. To learn more about this excellent thermometer and to also purchase one if you desire, just click on the underlined Thermapen Thermometer. When checking the temperature of your prime rib roast, insert meat thermometer so tip is in thickest part of beef, not resting in fat or touching bone. Cook until rib roast reaches an internal temperature of 1. F. or your desired temperature. See chart to determine Prime Rib Roast Internal Cooking Temperatures for rare, medium rare, medium, medium well and well done. Remove from oven, cover loosely with aluminum foil, and let sit approximately 1. Cutting into the meat too early will cause a significant loss of juice. Do not skip the resting stage. Residual Heat or Carry Over Cooking Remember, the rib roast will continue to cook as it sets. The internal temperature will rise to 1. F. to 1. 30 degrees F. If allowed to rest as long as an hour, the internal temperature will rise even higher. So, pay attention to how long you let the cooked prime rib roast sit. Holding Cooked Rib Roast To hold cooked roast until serving time, immediately turn off the oven and leave the door ajar after removing roast. Let roast sit 1. 5 minutes on the counter and then return roast to the oven, door closed, for up to an hour or even 2 hours for the biggest roasts. Check the temperature every 1. If will rise approximately 1. F. at first, then gradually subside. If Using a Convection Oven Using a convection oven can cut as much as 2. It is also easier for your roast to dry out and cook too much in the convection oven. Watch the roast carefully and please use a cooking thermometer to know when the roast is done and should be taken out of the oven. Back to the top. What Size of Prime Rib Roast to Buy A common question people ask is How much prime rib roast should I buy per person A full prime rib roast is seven 7 ribs, close to 1. The term standing means the bones are included in the roast, thus the roast can stand by itself. A prime rib roast comprises of seven ribs starting from the shoulder chuck down the back to the loin. Do not even bother with less than a three rib roast, any less than that is not a roast but rather a thick steak and would be better treated as such. For a generous serving of roast, figure on two people per rib. That means if you plan to serve two 2 people one 1 rib roastsix 6 people three 3 rib roasteight 8 people four 4 rib roastten 1. How To Purchase A Prime Rib Roast First of all, lets dispel a common myth The term prime rib does not necessarily indicate a rib roast is a prime grade, and in most cases, it probably is not. Angry Shrimp. Prime is an official USDA designation of grade and few supermarkets display this elite grade of beef because of its high cost relative to other grades. Prime Rib has become more a style of cooking the meat than of the quality of the cut. This is also why you rarely see this cut labeled as Prime Rib at the supermarket but rather as Beef Bone In Rib Roast because the USDA requires that a cut of beef must be officially graded as Prime before it can be so labeled. Insisting you get a rib roast that is actually prime grade is well worth the effort. Less than 2 of all industry beef merits this designation from the USDA. You will likely have to ask your butcher to special order a true Prime grade rib roast for your occasion, but when the forks hit the plate, your family and guests will notice the difference and then some One universal truth of the meat world is that fat means flavor But of course, many prefer a leaner cut, and the whole beef rib where rib roasts are portioned was kind enough to offer both. The whole piece is divided roughly in half, a large end and a small end. The large end is defined by the presence of more fat pockets throughout the meat, while small end rib roasts contain a single, intact muscle and are leaner. Whether one is better than the other is really never more than a matter of personal taste and how much fat your diet will tolerate. Garlic Prime Rib Recipe Allrecipes.