In a saucepan, melt butter over medium heat. Stir in flour, salt, and pepper until smooth. Gradually add milk, stirring constantly until thickened. Remove from heat and stir in cheese until melted.
Combine cauliflower, carrots, and cheese sauce in a baking dish. Bake for 20-25 minutes or until bubbly and golden brown.
Notes:
Feel free to add other vegetables like broccoli or peas.