Preheat oven to 210°C. Place pork on a rack over a roasting dish and put in oven. Roast for 15 minutes. Reduce temperature to 150°C and continue cooking for 45 minutes per 500g. To check pork is cooked, pierce the thickest part with a knife: if the juices run clear, the pork is cooked. Alternatively, pork is cooked when the thermometer shows 71°C.