HEAT FAT IN LARGE SAUTE PAN or Dutch oven with lid. Liberally salt and pepper both sides of meat and brown in hot fat on both sides until colored a deep mahogany. Add carrots and potatoes and sprinkle with rosemary, salt and pepper. Add onion slices and water. Reduce heat to simmer. Cook, covered, 30 minutes. Check for doneness by cutting into thickest part of roast. It usually takes 35 to 45 minutes for medium rare. Dont overcook. Remember that meat continues to cook a little after it is removed from stove. Arrange meat and vegetables on platter and serve hot. If you wish, you may sprinkle 3 tablespoons flour over pan drippings, place pan back over medium heat and cook, stirring constantly, until thick and smooth. Slowly add 2 cups water, stirring. Season to taste with salt and pepper. When thickened, transfer gravy to bowl and serve with roast and vegetables.