Lightly grease a 10-inch cast iron skillet; set aside. In a small bowl, mix together sugars and cinnamon; set aside. Place cinnamon roll pieces swirl-side-up and evenly spaced in pan. Brush the dough with 1 tablespoon of butter. Cover dough with sugar mixture, optional nuts, and drizzle with remaining butter. In a warm area, let rise until double in size. Bake in a preheated 325° convection oven (375° conventional oven) for 15-20 minutes or until light golden brown. Remove from oven. When cool, drizzle with icing if desired.