Preheat oven to 425°F. and butter twelve 1/3-cup muffin tins. In a bowl whisk together cornmeal, flour, sugar, baking powder, baking soda, salt, and Cheddar. In a small bowl whisk together buttermilk, egg, butter, and chilies. Add buttermilk mixture to cornmeal mixture, stirring until just combined, and stir in roasted peppers (do not overmix). Divide batter evenly among muffin tins and bake in middle of oven 15 to 20 minutes, or until golden and a tester comes out clean.