Preheat oven to 350 degrees. In a large bowl, mix ricotta, egg, half of the mozzarella, parmesan, parsley, salt, and pepper. Fill a large resealable bag with the ricotta mixture. Cut off one corner, large enough to fill the noodles.
In a 13x9-inch baking dish, spread half of the marinara sauce. Fill the manicotti by squeezing the ricotta mixture into each end of the noodle until full and place them into your baking dish. Repeat with remaining noodles. Pour the remaining marinara over the top and sprinkle with the remaining mozzarella over the top. Bake for 40 minutes, allowing to rest for 10 minutes before serving.