Cook rotini as directed on package, until al dente, about 7-8 minutes.
Meanwhile, heat olive oil in large fry pan. Add onion and celery to hot oil. Salt and pepper to taste. Saute until onions carmelize and turn translucent.
Add vegetables and chicken to the onion and celery. Mix well.
Pour cheese sauce over the top. Mix well, until chicken and vegetables are completely coated. Cover and simmer on low, stirring occasionally, about 5 minutes.
When rotini is ready, drain, and add to cheesy chicken and vegetable mixture. Fold in gently to completely coat the pasta with sauce.Cover and simmer on low, stirring once or twice, until heated through, about 15 minutes.
Sprinkle top with a shredded Parmesan.