For pot roast, the internal temperature indicates the level of doneness. Use a meat thermometer to measure the internal temperature. Remove the roast from the oven when the internal temperature reaches 145°F (63°C) for medium-rare, 160°F (71°C) for medium, or 170°F (77°C) for well-done. Ensure the thermometer is inserted into the thickest part of the roast, avoiding bones or fat. Reaching the desired internal temperature ensures a tender and juicy roast.