generously spray 6 quart slow cooker with nonstick cooking spray, set aside.
combine italian sausage, onion, green pepper and garlic in 12 inch skillet, cook over medium high heat, stirring occasionally, until sausage is cooked through (6-10 minutes). drain if necessary. add pasta and mix well.
combine all filling ingredients in medium bowl until well mixed.
spoon 1/4 meat mixture (about 2 cups) into prepared slow cooker, top with 3 lasagna noodles (break to fit).
spread with 1/4 cheese filling (about 3/4 cup), top with 3 cheese slices. repeat layers 2 more times. top with remaining noodles, remaining filling and meat mixture.
cover and cook on low for 4-6 hours or high heat for 2-4 hours, or until noodles are tender.
top with remaining 3 cheese slices. let stand until cheese is melted. cut lasagna into pieces or wedges.