Preheat oven to 375°F (190°C). Spray a 10x7 inch casserole dish with nonstick cooking spray. Place a foil-lined baking sheet on the lowest oven rack to catch drips.

In a large skillet, crumble and cook Italian sausage over medium heat, breaking it up with a spoon. Once cooked, remove sausage with a slotted spoon, reserving 1 tablespoon of drippings.

In the skillet with reserved drippings, add butter and minced garlic, sautéing for 30 seconds until fragrant. Slowly pour in heavy cream, whisking constantly. Add a pinch of red pepper flakes and black pepper. Simmer for 3-5 minutes until slightly thickened. Stir in Parmesan cheese until melted. Adjust seasoning with salt and pepper.

Spread a layer of Alfredo sauce in the casserole dish. Arrange a layer of ravioli, slightly overlapping. Sprinkle cooked sausage over ravioli, then drizzle with more Alfredo sauce. Add a layer of mozzarella cheese. Repeat layers, finishing with cheese on top. Sprinkle with Italian seasoning if desired.

Cover dish with foil sprayed with nonstick spray. Bake for 30 minutes. Remove foil and bake for an additional 10-15 minutes until cheese is bubbly and golden. Let rest for 10-15 minutes before serving.