Preheat oven to 375 degrees.
First, mix ricotta and pesto in a bowl.
Next, Pour 1/2 of the marinara on the bottom of a lasgana pan. Smear the sauce around to cover the whole dish.
Now, layer raviolis to cover the bottom of the dish.
Next, spread all the pesto ricotta cheese mixture ontop of the ravioli. Spread the ricotta around but dont worry about covering everything because it will spread more as it melts in the oven.
Now, add layer of mozzarella ontop of the ricotta.
Next, layer more frozen raviolis covering the whole dish.
Now, spread rest of marinara over raviloi and top with the rest of mozzarella cheese.
Finally, baked covered in tin foil for 30 minutes (on middle rack in the oven. Then bake uncovered at 450 degrees to melt the cheese and enjoy!