In a saucepan, melt butter with sugar. Do not overcook. Preheat oven to 350 degrees (if not preparing the night before). Grease a 9 x 12 casserole dish.
Transfer melted butter and sugar to a bowl. Beat in eggs, heavy cream, cinnamon, vanilla, & nutmeg.
Slice the cinnamon rolls into fourths. Mix cinnamon roll pieces into egg mixture. Toss thoroughly to coat. Pour the entire bowl of cinnamon roll pieces and egg mixture into the greased casserole dish, distribute evenly in casserole dish.
Sprinkle casserole with pecans. Bake for 35-40 minutes (or until casserole is browning and toothpick comes out clear.)
Remove casserole from oven. Warm icing in microwave for 15 seconds. Pour evenly over casserole.
When I prepare the casserole the night before, I cover it with foil and stick it in the fridge. I also omit the pecans until the morning of, and I sprinkle them over the casserole right before I bake it.