Lightly coat a 2-quart rectangular baking dish with cooking spray; set aside. Spread about 1/3 cup of the filling on each lasagna noodle. Starting from a short end, roll up each noodle. Place the lasagna rolls, seam sides down, in the prepared baking dish; set aside.
For sauce, lightly coat a medium saucepan with cooking spray. Heat skillet over medium-high heat. Add mushrooms and green onions; cook and stir about 3 minutes or until vegetables are tender. In a medium bowl stir together 1/4 cup of the evaporated milk and the flour until smooth; stir in the remaining evaporated milk and the salt. Stir the milk mixture into the mushroom mixture. Cook and stir until thickened and bubbly. Remove from heat. Stir in the remaining Swiss cheese until melted. Pour the sauce over the lasagna rolls.
Bake, covered, in a 350 degree F oven about 35 minutes or until lasagna rolls are heated through. To serve, sprinkle with paprika. Makes 8 servings.