Step 1

Place the diced tomatoes and their juices, crushed tomatoes, garlic, Italian seasoning, salt, and vinegar together in a large bowl and stir to combine.

Step 2

Coat a 6-quart or larger slow cooker with cooking spray. Pour 1 1/2 cups of the tomato sauce into the bottom of the slow cooker. Scatter 1/3 of the ravioli (about 3 1/2 cups) evenly over the sauce. Sprinkle 1/4 of the cheese (about 1 cup) over the ravioli. Repeat the layers of sauce, ravioli, and cheese two more times. Pour the remaining tomato sauce over the top, then sprinkle with the remaining cheese.

Step 3

Cover and cook on the LOW setting until the sauce bubbles, the ravioli is heated through, and the cheese melts and browns, about 8 hours. Sprinkle with the parsley if desired and serve.