Layer 3 lasagna noodles, broken into pieces to fit, over sauce in slow cooker. Top with one-third of the Alfredo sauce (about 1/2 cup), spreading to cover noodles completely. Top with 5 of the cheese slices, overlapping if necessary. Top with one-third of the vegetable mixture (about 2 cups), spreading evenly. Repeat layers twice. Sprinkle Parmesan cheese over top.