Boil chicken and debone. Cut into bite size pieces. Use the broth and add extra water if needed, to boil the noodles in. Saute mushrooms, pepper, onion and celery in butter. Add in chicken and slowly melt Velveeta cheese. Mix soups, Rotel and Parmesan cheese. (Leave about 1/4 cup Parmesan to put on top of casserole).
Drain the noodles and mix together. Pour spaghetti into a long casserole dish and bake at 350 degrees until bubbly brown about 30 minutes.