Layer the pasta, tomatoes, and cheese. Add uncooked pasta, marinara sauce, diced tomatoes, Italian seasoning, grated Parmesan, and 1 cup of shredded mozzarella to a 5-quart or larger slow cooker. Then, stir until everything is well mixed. After that, put small spoonfuls of ricotta cheese on top and gently mix it in. Sprinkle the remaining 1 cup of shredded mozzarella over the pasta mixture.