To add to what jennyema said, proper temperature is 140ºF. I would suggest putting some warm water in your slow cooker and checking the temperature after a hour or so to see if it will hold at that temp.
I did a little searching and on a couple sites for chefs, they suggested holding rice dishes covered in a warm oven and replenishing the serving dish occasionally, or keeping cooled cooked rice in the fridge and reheating in the microwave as needed.
The trouble with eating Italian food is that five or six days later you're hungry again. ~ George Miller