In a large skillet, cook beef, onion and garlic over medium heat 6-8 minutes or until beef is no longer pink, breaking up beef into crumbles; drain. Stir in spaghetti sauce., In a small bowl, mix ricotta cheese, Parmesan cheese, parsley and pepper. Spread 1 cup meat mixture onto the bottom of an ungreased 5- or 6-qt. slow cooker. Arrange 4 noodles over sauce, breaking noodles to fit if necessary; layer with half of the ricotta mixture, 2 cups mozzarella cheese and 1 cup meat mixture., Top with 4 noodles, spinach, Alfredo sauce and 2 cups mozzarella cheese. Continue layering with 4 noodles, remaining ricotta mixture, 2 cups mozzarella cheese and 1 cup meat mixture. Add any remaining noodles; top with remaining meat mixture and mozzarella cheese., Cook, covered, on low 4-5 hours or until noodles are tender.