Prep oven and baking dish: Preheat oven to 350°F (175°C). Grease a 9x13-inch ceramic or glass baking dish with butter or nonstick baking spray.

Cut dough and prep apples: Open cinnamon roll cans and reserve both containers of icing. Cut each cinnamon roll into 6 equal bite-sized chunks. In a small bowl, toss diced apples with melted butter, brown sugar, and cinnamon. Scatter half of the cinnamon roll pieces across the prepared baking dish, layer the spiced apples over them, and top with the remaining cinnamon roll chunks.

Whisk the custard: In a medium bowl, whisk together eggs, whole milk, heavy cream, maple syrup, vanilla extract, cinnamon, nutmeg, and sea salt until completely smooth.

Pour and soak: Pour the spiced custard evenly over the cinnamon roll chunks and apples in the dish, ensuring all dough pieces are moistened. Let sit for 5 minutes at room temperature so the dough absorbs the custard.

Bake to golden perfection: Bake in the preheated oven for 30 to 35 minutes, until the top is puffed and golden brown, and the custard center is softly set (a toothpick inserted in the center should come out clean of wet custard).

Glaze and garnish: While the bake is hot from the oven, microwave the reserved icing containers with 2 tablespoons of warm milk for 15 seconds until runny. Drizzle generously over the entire casserole, scatter with toasted chopped pecans, and serve warm with vanilla ice cream.