Place the roast in a roasting pan. Cover with the 2 cups water, ketchup, chili powder, sugar, and salt. Cook 1 hour in the preheated oven.
Place the potatoes, onion, and carrots in the roasting pan with the roast and liquid. Continue cooking 1 hour, or until the vegetables are tender and the internal temperature of the meat has reached a minimum of 145 degrees F (63 degrees C).
Remove the roast and vegetables from the pan, and drain the remaining liquid into a bowl. In a separate bowl, mix the flour and water. Stir into the remaining roast liquid to make gravy.
