Grease the interior of a 6-quart slow cooker with butter or cooking spray.

Open the cinnamon roll cans and cut each roll into quarters. Save the included icing packets for later.

Layer half the cinnamon roll pieces evenly across the slow cooker bottom.

Spoon half the apple pie filling over the first cinnamon roll layer.

Add the remaining cinnamon roll quarters to create a second layer over the apple mixture.

Whisk together eggs, heavy cream, brown sugar, vanilla, and cinnamon in a medium bowl until you achieve a smooth mixture.

Pour the custard mixture evenly over all the layered ingredients.

Cover and cook on LOW for 2½-3 hours, until the center feels firm when you insert a toothpick (it should come out mostly clean, not raw). Check earlier if your slow cooker runs hot.

While the casserole finishes cooking, make the icing by whisking butter and cream cheese until smooth.

Add cream gradually, then mix in powdered sugar until you create a well-blended icing.

Drizzle the warm icing over the finished casserole.

Serve immediately while warm. You can easily reheat leftover portions the following day.