I regularly use a roaster to keep rice warm.
First, start with either converted rice (UNcle Ben's type), brown rice, or Basmati. All three hold better than any others.
Second, cook it barely done, with just enough water/liquid to finish- no extra.
Third, preheat the roaster 20 minutes to 200 and spray with nonstick spray.
Fourth, add the rice, put a clean cotton dishtowel over the rice to catch any drip or moisture from condensation. Put the lid on. Turn to 180. It will hold an hour without mushing.
You must preheat the roaster and bring the water to a boil before adding the rice when you try to cook from scratch in the roaster, use the right rice, and cut the liquid about 10% from the usual, since the roaster holds moisture better. You also have to turn down to 180 as soon as done and put the cloth on
