In a bowl, stir together the ricotta, pesto, and 1/2 cup parmesan until combined; set aside.

Add 1 cup of the pasta sauce on bottom of slow cooker. Spread to coat the bottom of the slow cooker.

Next, place 1/2 of the bag of frozen ravioli in the slow cooker.

Take 1/2 of the ricotta mixture and spread it on top of the ravioli and the sprinkle with 1/2 cup of the mozzarella.

Repeat layers again (1 cup sauce, remaining frozen ravioli, remaining ricotta, remaining mozzarella).

Spread remaining sauce over top. Cook on low for 3 hours.

Remove lid and add sprinkle with remaining 1/4 cup parmesan. Replace lid and cook an additional 30 minutes on low. Serves 6.