Sweet Potato Casserole dishes can be made ahead of time and then placed in the refrigerator covered using some saran wrap or tin foil.
Then place the Sweet Potato Casserole into the microwave to reheat it or preheat the oven to 400 F and then place the Sweet Potato Casserole into the oven to reheat before serving.
It should only take around 30 minutes to an hour to reheat the Potato Casserole dish in the oven or 10 to 15 minutes to reheat the Sweet Potato Casserole dish in the Microwave.
Just be sure to keep an eye on it to avoid overheating it or drying it out.