Take a tablespoon or so of olive oil and spread all around the roast. Sprinkle around the roast with salt and pepper. Set the roast in the roasting pan. Cut the carrots into thirds. Cut the onions into halves. If you are using small potatoes, use whole potatoes. Respectively if using large potatoes cut them into halves or quarters. Arrange the vegetables around the meat and add the rosemary sprigs. Add 2-3 centimetres of water to the bottom of the pan. Cover with foil and cook on 180°C (375°F) for half an hour. Lower the heat to 110 C. The roast should take about 2 and a half hours additionally to cook. Check the temperature with a meat thermometer. Pull the roast from the oven when the inside temperature of the roast is 60-65°C. Let the roast rest for at least 15 minutes, tented in aluminium foil to keep warm, before carving to serve. For the gravy: Place the roasting pan with the drippings on the stove top at medium heat. Add some water, red wine, or beef stock to the drippings to deglaze. Dissolve a tablespoon of cornstarch in a little water and add to the drip pan. Stir quickly while the gravy thickens to avoid lumping. You can add a little butter if there is not a lot of fat in the drippings. Add salt and pepper to taste, and some fresh thyme.