Heat oven to 350° F. Bring a large pot of lightly salted water to boiling.
Add sausage to a large skillet set over medium heat. Cook 8 to 10 minutes or until browned, breaking apart with a wooden spoon. Stir in sage and cook 1 minute. Remove with a slotted spoon; set aside. Pour off and discard drippings.
In same skillet, whisk pumpkin, milk, Neufchâtel, egg yolks, 1 cup of the Asiago, the nutmeg, pumpkin pie spice and salt. Stir over medium heat until cheeses are melted.
Meanwhile, cook rigatoni in boiling water 1 minute less than package directions, about 9 minutes. Drain, reserving 1 cup of the pasta water. Return pasta to pot. Stir in sausage, pumpkin mixture and reserved pasta water. Mix well to combine. Transfer to a 13 x 9 x 2-inch dish and top with panko and remaining 2 tbsp Asiago. Bake at 350° F for 20 minutes. Turn broiler on HIGH and broil 1 to 2 minutes or until top is lightly browned.