Preheat oven to 500 degrees. Rub the pork with garlic. Pat on the rosemary and season with the salt and pepper. Lightly sprinkle the flour over the meat, shaking off any excess. Insert a meat thermometer into the center of the roast and place the meat in a large roasting pan on the bottom oven rack. Add a small amount of water in the pan.
Roast for 15 minutes, then reduce heat to 325 degrees and cook until the internal temperature reaches 165 to 170 degrees. Transfer to cutting board and cover with foil. Let sit 15 minutes before carving. Serves 6.
