Preheat oven to 350 degrees F. Spray a 9 x 13-inch baking dish with cooking spray and set aside.
Cook the pasta in a large pot of salted boiling water, until not quite al dente (about 9 minutes). Drain and rinse under cold water. Set aside.
Stir together ricotta, 6 tablespoons of Parmesan cheese, pesto and egg. Season with salt and pepper to taste. Set aside.
In a large skillet, brown sausage until no longer pink. Drain and return to the skillet. Stir in marinara sauce. Set aside.
Bring a pan of lightly salted water to a boil. Add the asparagus pieces, cook for 3-4 minutes until just tender. Drain and immediately transfer to a large bowl of ice water to stop the cooking. Let asparagus cool for 2-3 minutes. Drain the water and pat the asparagus dry. Add asparagus to the cooked pasta.
Spread a thin layer of the marinara sauce mixture in the bottom of the dish. Dot the surface with half of the ricotta cheese mixture. Ladle 2 scoops of the marinara sauce into the pasta and toss to combine. Spread the pasta and asparagus mixture in a single layer in the dish.
Pour remaining marinara sauce over the pasta. Dot with remaining ricotta mixture. Sprinkle with mozzarella and 2 remaining tablespoons of Parmesan.
Cover the ziti and bake for about 25-30 minutes (or until the casserole is hot and bubbly). Remove the cover and return the dish to the oven for about 10 more minutes, or until the top is lightly browned and the cheese is melted.