Preheat oven to 350.

Heat the milk in a small saucepan with the roux cubes, stirring frequently, until the cubes are fully melted and the milk comes to a simmer. As it starts to thicken, add the cheese, and continue stirring until it melts and the sauce has thickened. Set aside.

Place cauliflower in a 3-4 c baking dish, or two 1 cup ramekins. Pour cheese sauce over them carefully.

Bake at 350, for 15 minutes in ramekins or 20 minutes in a larger dish. Let rest a few minutes, then serve.