Preheat the oven to 375 degrees F. Coat a 3-4 quart baking dish with cooking spray.
Melt the butter in a large pot over medium heat. Add the flour, then whisk until combined, about 30 seconds.
Pour in the water and whisk until smooth and just thickened.
Add the milk and whisk until combined.
Stir in the pasta, salt, garlic powder, onion powder, smoked paprika and pepper, then bring the mixture to a simmer.
Cook for 10-12 minutes, stirring occasionally, until pasta is tender.
Turn the heat to low, then stir in 4 cups of cheddar cheese and the mozzarella. Keep stirring until the sauce is smooth.
Spread the pasta mixture into an even layer in the prepared baking dish. Sprinkle the remaining cup of cheddar cheese over the top.
Bake for 15-20 minutes or until cheese is melted and pasta is bubbling. Serve immediately.