Prep the baking dish: Grease a 9×13-inch baking dish lightly with butter or non-stick spray.
Cut the rolls: Cut each cinnamon roll into 4 quarters and arrange the pieces evenly in the prepared baking dish.
Make the caramel sauce: In a small bowl, mix together the melted butter, brown sugar, and ground cinnamon, then pour the mixture evenly over the cinnamon roll pieces.
Prepare the egg mixture: In a separate bowl, whisk together the eggs, heavy cream, and vanilla extract until well combined, and pour it over the rolls.
Refrigerate overnight: Cover the dish tightly with plastic wrap and place it in the refrigerator overnight so the rolls soak up all the rich flavors.
Bake: In the morning, preheat your oven to 175°C (350°F). Remove the plastic wrap and bake uncovered for 25 to 30 minutes, or until golden brown and bubbling.
Ice and serve: Drizzle the reserved icing packets from the cinnamon roll tubes over the warm casserole before serving.