Spray slow cooker crock with cooking spray.
Roll out dough to about 14x12-inches. Spread butter evenly on top of dough. Sprinkle with sugar followed by cinnamon.
Roll up jelly-roll style, tightly pinching ends so sugar and cinnamon doesn’t fall out. With a sharp knife cut into 1-inch sections, and lay into prepared crock. Allow dough to rise to double its size (around 2–4 hours).
Secure a paper towel under the lid of the slow cooker. Cover, and cook on high 2 hours.
For the frosting: Mix powdered sugar and milk to make a thick paste; adding more milk or powdered sugar as needed. Spread on still-warm rolls, allowing the frosting to melt slightly. Serve warm.