Add chicken, cream of chicken soup (do not add water), chicken broth, pepper, oregano, garlic powder, and onion powder to your slow cooker. Cook on low for 6-7 hours or on high for 4-5 hours. Remove chicken once cooked, shred, and return to slow cooker.
Meanwhile, cook Rotini according to package directions and set aside.
Add sour cream, 1 cup cheese, and cooked and drained pasta to your slow cooker. Top with remaining cheese then cook for an additional 20 minutes on warm.