Cook the ziti according to the package directions. Drain well and set aside.
Cook the sausage links in oil in a large skillet for 15 minutes or until browned over medium heat; reduce heat if necessary to keep them from burning. Drain well on paper towels. Slice the sausage diagonally and set aside.
Melt the butter in a heavy saucepan over low heat; add the flour, stirring until smooth. Cook for 1 minute, stirring constantly. Gradually add the milk; cook over medium heat, stirring constantly, until the mixture is thickened and bubbly. Stir in 1/4 cup Parmesan cheese, 1 tsp salt, and 1/2 tsp pepper. Add the ziti; stir well, and set aside.
Combine the remaining 1/4 cup Parmesan cheese, ricotta (or cottage cheese), egg, parsley, 1 tsp salt, and 1/8 tsp pepper. Stir well.
Place half of the macaroni mixture in a lightly greased 13 x 9 x 2 inch baking dish. Top with the ricotta cheese mixture and half of the sausage. Top with the remaining ziti mixture and sausages. Sprinkle with the mozzarella and paprika.