1Spray bottom of 5- to 6-quart slow cooker with cooking spray. Line side of slow cooker with foil; spray foil with cooking spray.
2In 12-inch skillet, cook sausage over medium heat 8 to 10 minutes, breaking up sausage with spoon, until no longer pink; drain. Place sausage in large bowl. In same skillet, cook beef, onion and garlic over medium heat 8 to 10 minutes, stirring occasionally, until beef is thoroughly cooked and onion is tender; drain. Add beef mixture and 1 jar of the pasta sauce to bowl with sausage; stir to combine.
3In slow cooker, spread half of remaining jar of pasta sauce to cover bottom. Layer with half of the ravioli and half of the meat mixture. Sprinkle with 1 1/2 cups of the cheese and half of the pepperoni. Repeat layers.
4Cover; cook on Low heat setting 3 hours. Sprinkle with olives before serving. Garnish with basil.