Follow the cooking instructions on the package of lasagna noodles.
In the meantime, in a large bowl, stir together the ricotta, one cup of the parmesan, spinach, onion, garlic, chili flakes, oregano, basil, salt, and pepper. Set aside.
Prepare a large baking dish, approximately 9x13 inches, by pouring the entire contents of the jar of sauce into the dish. Evenly spread the sauce around to coat the bottom of the baking dish. Set aside.
Once the noodles are cooked, lay each noodle flat on a cutting board.
Spoon 2 tablespoons of the spinach mixture onto each lasagna noodle. Spread the mixture evenly over the noodle, making sure to get to the very end, yet leaving at least 1 inch free of filling at the end.
Begin to roll up the noodle starting at the end with the filling. Don't roll too tightly, be sure to keep the filling inside the noodle.
Position the noodle in the prepared baking dish with the seam side facing down.
Once done, cover with aluminum foil and bake for 30 minutes.
Remove the foil, top with half of the remaining parmesan and place the baking dish under the broiler for 2-3 minutes.
Sprinkle with fresh parsley, more parmesan cheese, and serve immediately.