Cook sausage in a large nonstick skillet over medium-high heat, stirring until sausage crumbles and is no longer pink. Remove from pan; drain well, pressing between paper towels.
Make cheese sauce. Melt butter in a heavy saucepan over medium-low heat; whisk in flour until smooth. Cook, whisking constantly, 1 minute. Gradually whisk in milk; cook over medium heat, whisking constantly, 5 minutes or until thickened. Gently fold in 1 1/2 cups Cheese Sauce and sausage into egg mixture.
Spoon about 1/3 cup egg mixture down the center of each flour tortilla; roll up. Place, seam side down, in a lightly greased 13- x- 9-inch baking dish. Pour remaining Cheese Sauce evenly over tortillas; sprinkle evenly with Monterey Jack cheese.
Bake at 350° for 30 minutes or until sauce is bubbly. Serve with desired toppings. Toppings: halved grape tomatoes, sliced green onions, chopped fresh cilantro