Grease a 9×13-inch baking dish with butter or cooking spray. Slice each cinnamon roll into quarters and distribute evenly across the dish.

In a medium bowl, whisk together the eggs, milk, maple syrup, and vanilla extract until smooth. Pour evenly over the cinnamon rolls.

Mix cinnamon and sugar in a small bowl. Sprinkle over the assembled casserole. Cover tightly and refrigerate for at least 6 hours or overnight.

Preheat the oven to 350°F. Let the casserole sit at room temperature for about 10 minutes, then bake uncovered for 35 to 40 minutes, until golden brown.

Remove from the oven, drizzle with reserved icing, and let cool slightly before serving.

Slice and serve warm, optionally with fresh fruit or breakfast meats.