Preheat oven to 350F. Melt 3 Tbsp. of the butter in large saucepan on low heat. Stir in flour and seasonings. Cook and stir 2 minutes or until bubbly. Gradually add milk, stirring until well blended. Cook on medium heat until mixture boils and thickens, stirring constantly. Reduce heat to low; simmer 5 minutes.
Pour over shells in large bowl.
Add ricotta cheese; mix lightly.
Spoon half of the pasta mixture into 2-quart casserole dish; sprinkle with 1-1/2 cups of the pizza shreds. Cover with remaining pasta mixture and pizza shreds; top with tomato slices. Melt remaining 2 Tbsp. butter.
Mix with bread crumbs, Parmesan cheese and parsley; sprinkle over tomatoes.