Preheat oven to 375 degrees and bring a large pot of water to a boil.
Once the water comes to a boil, heavily salt the water and add in the shells. Cook for 9 minutes and then drain.
In a large bowl, mix together the ricotta, egg, Parmesan, garlic, parsley, red pepper flakes, oregano, salt and pepper.
In a 2-quart baking dish, spread ½ cup marinara sauce on bottom of pan.
Spoon the ricotta mixture into the cooked shells and place into prepared baking dish.
Top with the remaining marinara sauce. Sprinkle with the Mozzarella cheese.
Bake for 30 minutes, or until cheese is melted and browned.