In a medium bowl, mix the ricotta cheese, dried oregano, garlic powder, salt, and black pepper until well combined. Set aside.
Spray the inside of the crockpot with cooking spray to prevent sticking.
Begin layering: Start with a layer of marinara sauce at the bottom of the crockpot.
Add a third of the frozen ravioli on top of the sauce, followed by half of the ricotta mixture, and a third of the mozzarella cheese.
Repeat the layers: Add another layer of marinara sauce, followed by the remaining ravioli, the rest of the ricotta mixture, another third of mozzarella, and finish with a final layer of marinara sauce.
Top the last layer of sauce with the remaining mozzarella and sprinkle grated Parmesan cheese on top.
Cover the crockpot and cook on low for 4-5 hours or until the ravioli is cooked through and the cheese is melted and bubbly.
Once done, turn off the crockpot and allow it to sit for about 10 minutes before serving.
Before serving, garnish with fresh basil leaves if desired.
Notes
Serve directly from the crockpot in bowls, and finish with a sprinkle of extra Parmesan and fresh basil for a pop of color.