Both pork roasts and sirloins should be cooked to an internal temperature of 145 degrees Fahrenheit as determined by a digital thermometer, and both cuts of pork will take 4 to 6 hours on high or 8 to 10 hours on low to reach this temperature in a slow cooker. Follow the recipe's cooking instructions, but ensure the meat reaches 145 F internally, and allow it to sit for 3 minutes before serving.
When cooking full meals in a slow cooker, the meat and vegetables may cook at different temperatures, so it is recommended to first cut the meat into chunks so that it cooks at the same rate as the vegetables. If cooking the pork separately, leave it whole and add 1 cup of white wine, chicken broth or water with the meat in the pot and cover and cook. Remove the meat as soon as it reaches the required internal temperature to ensure it remains juicy and moist.
Pork loin roasts and sirloin tip roasts can also be roasted in the oven, and the cooking times are the same for both cuts of meat. Preheat the oven to 325 F and season the meat as desired. Cook in a shallow roasting pan for 1 hour to 1 1/2 hours, ensuring the meat reaches the proper internal temperature.