Preheat the oven to 400°F. On a flat baking sheet place the veal bones, carrots, onions, leeks, celery, parsley, bay leaves, thyme, and garlic. Roast them for 30 to 45 minutes, or until they are dark brown on all sides. Remove the veal bones and set them aside. Spread the tomato paste on top of the browned vegetables. Roast them for 30 minutes more, or until the tomato paste has turned a very dark brown. In a large stockpot place the roasted veal bones and vegetables. Cover them with water. Bring the liquid to a boil. Skim off any foam that appears on top. Reduce the heat to low and simmer the ingredients for 12 to 16 hours, or until the liquid is reduced by 1/2. Strain the liquid.