Cut 10 deep slits in roast; place a garlic clove in each slit. Combine the rosemary, 1 teaspoon onion powder, garlic powder and thyme; rub over entire roast. Cover; refrigerate for 2 hours., Add 1/2 in. of water to a roasting pan. Place the roast, carrots and onions in pan. Cover and bake at 325° for 2-1/2 to 3 hours or meat is tender. Remove meat and vegetables to a serving platter; keep warm., Strain drippings into a measuring cup. In a large saucepan, combine 3 cups drippings, bouillon, browning sauce and remaining onion powder. Combine cornstarch and cold water until smooth; stir into drippings. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with roast.