Preheat the oven to 425 degrees.
Add the chicken in a layer in the bottom of a well-greased 9x13 baking dish.
Place the butter and flour in a saucepan over medium heat on the stove. Whisk until combined and the butter is melted.
Slowly whisk the milk into the mixture in the saucepan until well combined. Continue to saute until it thickens.
Remove from the heat and stir in the ranch dressing as well as salt and pepper to taste.
Pour the sauce mixture over the chicken in the baking dish.
Sprinkle 1 cup of the cheese over the sauce.
Layer the tater tots on top of the chicken mixture.
Bake for 20 minutes.
Remove and layer with the bacon crumbles and remaining cheddar cheese. Bake for another 15-20 minutes until the tater tots are cooked completely and crispy.
