Heat the reserved sun-dried tomato oil in a large Dutch oven over medium heat. Add the onion and garlic; cook, stirring often, until softened (about 3-4 minutes).
Stir in sun-dried tomatoes and tomato paste, cooking until the paste deepens in color (about 2 minutes).
Pour in the chicken broth and heavy cream. Stir in basil, salt, Italian seasoning, garlic powder, and crushed red pepper. Bring to a boil over medium-high heat.
Add uncooked pasta and cook, stirring occasionally, until al dente (about 10 minutes).
Stir in spinach, rotisserie chicken, cream cheese, and Parmesan. Cook until the cheeses melt and spinach wilts (about 5 minutes).
Ladle into bowls and garnish with extra Parmesan, basil, and crushed red pepper if desired.