Place frozen vegetables in a 3-1/2- or 4-quart slow cooker. Top with meat. In a medium bowl combine stir-fry sauce, water, and, if desired, crushed red pepper. Pour over meat and vegetables in cooker.
Cover and cook on low-heat setting for 9 to 10 hours or on high-heat setting for 4-1/2 to 5 hours. Discard spice packet from ramen noodles. Stir noodles into meat mixture in slow cooker. Cover and let stand 10 minutes. Stir before serving. Makes 4 to 6 servings.