Hello ThriftyChef, thank you for reaching out about this important safety concern. In the world of kitchen safety and organization, we often discuss the risks associated with certain starch-heavy foods.
Unfortunately, it is not safe to eat rice that has been left at room temperature overnight. Rice contains spores of a bacterium called Bacillus cereus. These spores are capable of surviving the cooking process. If the rice remains between 4°C and 60°C for more than two hours, the spores can grow into bacteria and produce heat-resistant toxins.
Even if you reheat the rice thoroughly, these toxins will remain and could lead to food poisoning. For your health and safety, I strongly recommend disposing of the rice.