In a medium sized bowl, mix together the ricotta, frozen chopped spinach, and Italian seasoning.
Then, top with one cup of the mozzarella cheese.
Layer the remaining ravioli on top of the shredded cheese, then pour on the rest of the pasta sauce and remaining ricotta mixture.
Place a layer of plastic wrap directly on top of the casserole, then cover the entire pan with foil.
Preheat the oven to 400°. Remove the foil and take off the plastic wrap, then replace the foil.
Alternately, you can bake this dish from frozen at 375° for 1 1/2 hours.