Preheat oven to 375 degrees.
Bring a large pot of water to boil and cook the spaghetti while preparing the rest of the recipe.
Debone the rotisserie chicken and add chicken to a large bowl. Pour over 1/4 cup chicken broth to moisten the chicken, then sprinkle over cajun seasoning, about 2 tablespoons or enough to evenly coat the chicken.
In a large bowl, make the sauce by adding cream of chicken, rotel (undrained), sour cream, garlic, 1 tablespoon cajun seasoning, 1/2 tsp seasoning salt, 1/2 tsp red pepper flakes, 1/2 tsp freshly cracked pepper. Whisk it together until smooth.
Heat 3/4 cup of chicken stock in the microwave for 1 minute (or until warmed through), then pour into the mixture and whisk together.
Into a 9x13 casserole dish, add drained spaghetti, seasoned chicken, sauce mixture, and half the cheese. Mix it all together using tongs to ensure the sauce evenly coats the pasta and that the chicken is distributed evenly.
Top it off with the remaining cheese and sprinkle with dried parsley. Cover with foil (spray with nonstick spray to prevent cheese from sticking to foil). Bake for 25 minutes. Remove foil and bake for an additional 10 minutes or until cheese is melted and edges are browned and bubbly.