Beef roasts are among the safest cuts of meat in terms of bacterial growth because less of the meat is exposed to air than smaller cuts or ground beef. Yet it's still important to cook them quickly after you bring it home from the store. Properly refrigerated, a roast will keep for a few days. It's OK to bring a roast to room temperature for an hour before you cook it, which can help it brown and cook more evenly. Otherwise, it must stay chilled.
In general, cook a beef roast within three to five days of purchase, according to the USDA. This shelf-life depends on proper storage, however. When you're at the grocery store, hit the meat department last so the roast stays as cold as possible. Pack the roast in a cooler if it will take more than 30 minutes to get home. Keep a collapsible fabric cooler in your trunk for this purpose. Once you get home, refrigerate the roast immediately in a refrigerator set at 40 degrees Fahrenheit. You can keep the meat in its original wrappings, but store it in the coldest part of the refrigerator or in the meat drawer.
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If the meat was properly processed and packaged, and you refrigerated it promptly, it should be just fine for three to five days. Inspect it before you cook it. Any beef that has a pronounced off-odor may have spoiled and should be discarded or returned to the store. Beef that has darkened or changed color isn't necessarily spoiled, but if it has a slimy texture or signs of mold in addition to an odor, don't cook it.
If you can't use the meat within three to five days, pack it into the freezer quickly for longer storage. Foods frozen at 0 F will stay safe and fresh indefinitely, but the quality begins to decline after a few months. To keep the roast tasting fresh and juicy, remove it from its wrappings if you plan to store it longer than two weeks. Wrap it in butcher's wrap, plastic wrap or aluminum foil, or use plastic freezer bags or vacuum-seal bags. Write the date on the package, as well as the weight of the roast. When packaged properly, roasts can remain frozen for four to 12 months.
When beef is left at room temperature, or temperatures between 40 and 140 F, bacteria multiply quickly and increase the risk of foodborne illness. This is why it's important to refrigerate roasts as soon as you get home. It's also important to refrigerate any leftovers promptly to keep them safe. Refrigerate leftover roast beef within two hours of serving it. Reduce this time to one hour in hot weather. Wrap the roast beef tightly in plastic wrap or place it in covered containers. Store it in a refrigerator set at 40 F and eat it within two to three days.