Preheat the oven to 375 degrees F (190 degrees C).  Spray cauliflower florets with cooking spray and season with salt and pepper; place on a baking sheet.  Roast in the preheated oven for 30 minutes.  Meanwhile, heat half-and-half in a saucepan over medium-low heat. Add Mexican, Cheddar, and cream cheeses slowly, stirring to combine, until melted.  Butter an 8×10-inch baking dish.  Mix roasted cauliflower with cheese sauce. Transfer to the prepared dish.  Bake in the preheated oven until bubbly, about 15 minutes.