Preheat oven to 375°F. Cook ziti until just al dente, about 2 minutes less than package directions. Drain and set aside.
Brown Italian sausage in a skillet over medium heat, breaking it up, about 7 minutes. Drain fat.
In a large bowl, mix ricotta, egg, garlic powder, Italian seasoning, salt, and pepper. Stir in 1 cup mozzarella.
Combine cooked pasta, sausage, marinara sauce, and ricotta mixture in the bowl and stir to combine.
Transfer to a greased 9x13 baking dish. Top with remaining mozzarella and Parmesan.
Bake uncovered for 25-30 minutes until cheese is melted and edges are bubbling.