Remove the cinnamon roll dough from the first tube, and stack them one on top of the other. Press down, and using a rolling pin, roll into a uniform shape, about 7" in diameter.
Grease your cast-iron skillet well with non-stick cooking spray, or brush with vegetable oil.
Lay the first layer of rolled-out dough into the pan. Brush with a little melted butter, top with crushed graham crackers, chopped chocolate, and mini marshmallows.
Repeat the rolling process for the second layer. But score the dough halfway through (do not cut all the way through!) with a sharp knife, forming a diamond pattern. Place on top of the first layer, brush with melted butter and top with graham cracker crumbs. Carefully wedge the marshmallows into the scored bits of dough. Top with chocolate. Set aside.
Preheat your grill for 325 degrees F.
Once up to temperature, place the pan into the grill, close the lid, and cook for 40-45 minutes, or until the dough is longer raw and sticky. It should be golden brown, with toasted marshmallows on top.
Remove pan from grill, and let the cake cool for 15 minutes. Using a spatula, remove the s'mores cake from the pan and place it onto a cutting board. Drizzle with warmed icing, cut into 6-8 slices, and serve with vanilla ice cream.