Melt butter. Add the flour and whisk for 1 min. Add cashew milk and nutritional yeast. Boil while whisking until thickened. Remove from heat. Stir in spices. Set aside.
Add roasted cauliflower to a greased baking dish. Pour the sauce on top. Sprinkle nutritional yeast and breadcrumbs on top. Bake at 375° for 25-30 min.