Boil the rotini until it is nice and al dente', then drain, and set to the side.
Next toss all of the chopped onions, peppers, garlic, and mixed vegetables into a large mixing bowl.
Next add in the tuna, and 3/4 cup of sharp cheddar cheese.
Now add in the alfredo sauce, and cream of mushroom soup.
Fold the ingredients, then add in the rotini.
Sprinkle in the salt & pepper.
Fold everything until well combined.
Preheat your oven to 375 F.
Butter a medium sized casserole dish.
Add the tuna casserole mixture into the dish, spread throughout the dish.
Sprinkle the remaining cheese on top of the casserole.
Sprinkle on the crouton crumbs OR seasoned bread crumbs, then the parsley flakes.
Leave the casserole uncovered, and bake for 40 minutes.
Let sit for 10 minutes before serving.