A portion of this cut that includes one rib makes two generous servings. If you don’t want to have leftovers, figure the number of people you will be serving, divide the number in half, and buy a roast with that many ribs. Look for rib roast that has a clear, red color. Beef normally has a purple-red color, but when exposed to oxygen it takes on a cherry-red hue known as the “bloom.” While the exterior is bright red, the interior of the meat retains the darker color. Vacuum-packed rib roast also shows this purplish color. Packaged rib roast should be cold and the packaging free of punctures or tears; vacuum-packed roast should have its seal intact. The beef should be firm to the touch. Check the label for the “sell-by” date and make sure to buy it before or on that date.