Spray a 12-cup bundt pan with nonstick cooking spray.
Open each can of cinnamon rolls. Reserve the icing for later. Cut each roll into 4 pieces.
Place the granulated sugar and 1 teaspoon pumpkin spice in a gallon size resealable bag. Add the cut-up cinnamon rolls (the pieces will fall apart a little) to the bag. Seal and shake to coat the pieces with cinnamon sugar.
Stir together the brown sugar and melted butter.
Place rolls in pan and drizzle with melted butter mixture.
Bake at 350°F for 40-50 minutes or until the top is a dark golden brown and the rolls are cooked through.
Cool 5 minutes then invert the monkey bread onto your serving plate. Do this carefully: the pan is hot!
Stir remaining ½ teaspoon pumpkin spice into the icing that came with the cinnamon rolls. Drizzle icing over the top of the monkey bread and serve warm.