Preheat oven to 375°. Cook rigatoni according to package directions., Meanwhile, in a large skillet, cook pancetta over medium heat until crisp, stirring occasionally. Remove with a slotted spoon; drain on paper towels. Discard drippings; wipe skillet clean., In same pan, heat butter over medium-high heat. Add onion; cook and stir until tender. Stir in flour, salt and pepper until blended; gradually whisk in milk. Bring to a boil, stirring constantly; cook and stir until thickened, 2-3 minutes. Remove from heat. Stir in cheese blend until melted., Stir in artichokes, spinach and pancetta. Drain rigatoni; add to cheese sauce. Transfer to a greased 13x9-in. baking dish; sprinkle with Parmesan cheese., Bake, uncovered, until golden brown and bubbly, 20-25 minutes.