Pour enough olive oil into a frying pan to reach a depth of 2 inches. Heat the oil over medium heat until a deep-fry thermometer registers 325 degrees F.
While the oil is heating, put the buttermilk and bread crumbs in separate shallow bowls. Working in batches, dip ravioli in buttermilk to coat completely. Allow the excess buttermilk to drip back into bowl. Dredge ravioli in the bread crumbs. Place the ravioli on a baking sheet, and continue with the remaining ravioli.
When the oil is hot, fry the ravioli in batches, turning occasionally, until golden brown, about 3 minutes. Using a slotted spoon, transfer the fried ravili to paper towels to drain.
Sprinkle the fried ravioli with Parmesan and serve with a bowl of warmed marinara sauce for dipping.