Cook pasta according to package directions. Meanwhile, in a large bowl, combine the chicken, cheese blend, spinach, tomatoes, Alfredo sauce, milk and pesto. Drain pasta and add to chicken mixture; toss to coat.
Transfer to two greased 8-in. square baking dishes. In a small bowl, combine the bread crumbs, Parmesan cheese and oil; sprinkle over casseroles.
Cover and freeze one casserole for up to 3 months. Cover and bake the remaining casserole at 350° for 40-45 minutes or until bubbly.
To use frozen casserole- Thaw in the refrigerator overnight. Remove from the refrigerator 30 minutes before baking. Cover and bake at 350° for 50-60 minutes or until bubbly. Yield- 2 casseroles (6 servings each).