Preheat oven to 350°F (175°C) and grease a 9x13-inch baking dish
Separate icing from cinnamon rolls and set aside
Cut each cinnamon roll into quarters and spread evenly in the dish
Whisk eggs, milk, cream, sugar, vanilla, and cinnamon until smooth
Pour custard evenly over cinnamon roll pieces
Gently press rolls down to absorb liquid
Sprinkle optional add-ins over the top
Bake uncovered for 35–40 minutes until center is set and top is lightly golden
Rest for 10 minutes, warm icing, and drizzle over casserole