Cook cannelloni according to package directions; drain and set aside.Combine tomato sauce and 2 tablespoons Parmesan cheese; spread 1 cup tomato mixture in a lightly greased 13- x 9- x 2-inch baking dish; set aside dish and remaining sauce.Cook beef, onion, and garlic in a large skillet until beef is browned, stirring to crumble meat; drain well.
Add spinach; saute 3 minutes. Add 1/3 cup Parmesan cheese, milk, eggs, and oregano; stir well. Stuff cannelloni shells with beef mixture. Place filled cannelloni on tomato mixture in baking dish; set aside.Melt butter in a heavy saucepan over low heat; add flour, stirring until smooth. Cook 1 minute, stirring constantly.
Gradually add half-and-half; cook over medium heat, stirring constantly, until mixture is thickened and bubbly. Stir in pepper. Pour over cannelloni; spoon remaining tomato mixture over cream sauce. Bake, uncovered, at 375° for 20 minutes. Yield: 6 servings.