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.