Preheat oven to 350 degrees. In a Dutch oven, heat oil over medium-high heat. Sprinkle roast all over with 1 teaspoon salt and 1/2 teaspoon pepper. Place in pan, and brown on all sides, about 10 minutes.

Turn meat fat side up. Add stock, wine, if using, onions, garlic, bay leaves, and thyme. Stir in tomato paste. Bring to a simmer, cover; put in the oven, and roast for 3 hours. Add carrots and potatoes, and cook until vegetables are tender, about 1 hour more.

Transfer the roast, carrots, and potatoes to a platter. With a spoon, skim the fat off the surface of the cooking liquid. Cut the roast into thick slices, and serve with the vegetables. Pass the pan juices separately.