In a large pot, bring salted water to a boil. Add the rotini pasta and cook according to the package instructions until al dente. Drain and set aside to cool slightly.
In a large mixing bowl, combine softened cream cheese, ranch dressing, olive oil, garlic powder, onion powder, and a pinch of salt and pepper. Mix until smooth and well-blended.
Add the drained rotini pasta to the ranch mixture, along with shredded chicken (if using), frozen mixed vegetables, and 1 cup of shredded cheddar cheese. Stir gently until thoroughly coated.
Lightly grease a 9x13 inch baking dish with cooking spray or olive oil. Pour the pasta mixture into the dish, spreading it out evenly.
Evenly sprinkle the remaining 1 cup of shredded cheddar cheese and grated Parmesan cheese on top.
Bake in the preheated oven for 25-30 minutes, until the cheese is bubbly and golden brown.
Remove from the oven and let cool for about 5 minutes. Garnish with chopped fresh parsley before serving.
Notes
Serve directly from the baking dish or spoon portions into individual bowls.