In the same skillet over medium heat, melt butter.
Add the flour and whisk constantly for 1-2 minutes (or until the mixture turns light brown).
Reduce the heat to low and slowly drizzle in the warm milk, whisking constantly for about 3-5 minutes, or until thickened.
Add the salt, garlic powder, and ranch seasoning. Stir to combine and remove from heat.
Add the cheeses, stirring to melt.
Add the cooked pasta, and toss to coat.
Season to taste with salt and pepper, and top with the chicken, bacon, and chopped parsley.