Pork roasts, as a large cut, can take a long time to defrost, but can be safely and successfully cooked from frozen. Frozen pork roasts cannot be crusted or marinated while frozen, so season your roast before freezing or brush with a glaze while cooking.
Pork roasts come in a range of sizes and shapes; the cooking time required varies depending on the cut and size of the roast. In general, frozen pork roasts take at least 50 percent longer to cook than a fully defrosted roast of similar size and shape. For a 1 1/2 pound frozen pork tenderloin roasted uncovered at 350 degrees Fahrenheit, the cooking time is around 60 minutes compared to 40 minutes for a defrosted tenderloin. In comparison, pork sirloin roasts, which have more fat than tenderloin and sometimes come with the bone-in, can take 1 hour and 35 minutes to cook in a 375 F oven. When cooked from frozen, they can take upwards of 2 hours and 15 minutes at the same oven temperature.
Methods and Temperature
Cooking pork roasts from frozen means you need to have a high enough cooking temperature to ensure that the roast defrosts and cooks at a steady rate. Too high a temperature leads to an overcooked, dry exterior, while too low a temperature means there is an increased risk of harmful bacteria developing. Cook all frozen pork roasts at temperatures no lower than 325 F.
Frozen pork roasts can be cooked on the stove top; in a convection or regular oven; in a Dutch oven; or on a grill over indirect heat. All methods use moderate, steady cooking temperatures. Pork roasts should never be cooked from frozen in a slow cooker.
To bake a frozen pork roast, preheat the oven to 350 F, and place your roast in a shallow pan in the center of the oven. For a larger, thicker, tougher cut, such as a pork shoulder, cook uncovered for around 45 minutes per pound. This means a 3-pound pork shoulder should be ready in 2 1/4 hours. Rotate the shoulder every 20 minutes to ensure even heating if you are not cooking with a convection oven. Because of the long cooking times, baste your roast with juices from the pan as it cooks. Fattier cuts, such as shoulders, require less basting than leaner ones, such as tenderloin. Let your roast rest for 3 to 10 minutes before slicing and serving.
Doneness and Serving
Pork, regardless of cut, is fully cooked when the internal temperature reads 145 F on a quick-read thermometer. While the roast firms up and turns white when cooked, these are not necessarily accurate indicators of doneness. At 145 F, pork roast is still slightly pink in the middle, although juices run clear. The only way to ensure doneness -- very important for cooking a roast from frozen -- is to use a quick-read thermometer. Slice pork roasts across the grain, using thinner slices for fattier, richer cuts of pork, and serve warm or at room temperature. Leftover cooked pork roast can be stored, well-wrapped, in the fridge for two to three days.