In a sauce pan over medium heat combine oil and flour. Stir for 2-3 minutes.
Whisk in flour and continue heating over medium heat stirring for 2-3 minutes.
Add minced garlic and stir for 30 seconds.
Whisk in milk. Continue cooking over medium heat, stirring often. When milk begins to simmer, it will begin to thicken. Do not boil.
Once milk is thickened, add salt, pepper, Italian seasonings and red pepper flakes.
Turn heat to low and whisk in Monterey Jack cheese and 1/4 cup Parmesan cheese.
Add tomatoes and chicken. Fold in carefully.
Place cooked pasta in a large bowl. Pour cheese mixture over pasta and stir carefully so all pasta is coated with sauce.
Spray two 9 x 11 inch casserole dishes with a non stick spray. Divide pasta mixture evenly into both dishes.
Top with remaining 1/4 cup Parmesan cheese
Bake uncovered in a preheated 400 degree oven for 40 minutes until hot and bubbly.
Remove from oven and let cool for 10 minutes before serving.
Add chopped parsley before serving (optional)