A roasted potato on a fork
The Best Way To Reheat Roasted Potatoes And Maintain Crispiness
Southern Living explains it's best to use the same method to reheat food as you cooked it, so for leftover roasted potatoes, you'll want to reheat them in the oven.
To get those potatoes crisp again, reheat them in a 400-degree oven covered in tin foil until warm, then remove the foil for a final few minutes to allow the skin to crisp back up.
Whether small cubes, wedges, or whole baked potatoes, reheating in the oven will help your roasted potatoes become crispy on the outside while remaining soft on the inside.