Preheat your oven to 375°F (190°C). Grease a 9x13 glass baking dish with melted butter to prevent sticking.
Cut each cinnamon roll into 8 equal pieces. Spread the pieces evenly over the bottom of the greased baking dish.
In a mixing bowl, whisk together the eggs, milk, cinnamon, and vanilla extract. Ensure everything is well combined for a smooth custard consistency. Pour this mixture evenly over the cinnamon roll pieces.
Drizzle 1 cup of maple syrup over the entire mixture.
Place the dish in the preheated oven and bake for 25 minutes until the top is golden brown and slightly puffed.
Remove the casserole from the oven. Drizzle the icing from the cinnamon rolls on top while it is still warm. Serve immediately for the best taste and texture.