In a large pot of salted water, cook the rigatoni al dente. You still want it to have a bit of a bite to it since it will continue cooking in the oven. If the package recommends 13 minutes boil time, only cook it about 9 minutes. Drain and set aside.

While the pasta is cooking, cook the Italian sausage in a large skillet over medium high heat. Combine ground pork, paprika, salt, fennel seeds, red pepper flakes, garlic and onion. Stir frequently while cooking and cook until sausage is browned and crumbly, 10-15 minutes. Remove from heat and transfer sausage to a paper towel lined plate. Discard grease.

In a large sized bowl, combine ricotta, egg, basil, oregano, and garlic powder. Stir to combine. Add 3 cups pasta sauce, reserving remaining 1 1/2 cups. Add cooked sausage and al dente pasta to bowl. Stir to combine. Transfer to a casserole dish.

Cover pasta mixture with remaining pasta sauce and top with mozzarella. Cover with oven safe lid or aluminum foil.

At this point you can either refrigerate until ready to bake or you can immediately transfer to oven.

Bake in preheated 350 degree F oven for 20 minutes covered (longer bake time required if previously refrigerated). Remove cover and bake additional 5-10 minutes to melt cheese.