This role is needed for events that will have food, be it snacks or a full catered meal.
For smaller events, a 'pot-luck' approach may be feasible, where participants are each asked to bring some food or drink to share. Create a 'Food' column on the registration page on the wiki. The food czar is responsible for making sure that enough quantity and variety will be brought to the event, including utensils and napkins.
The food czar should not be buying more than his share. You don't want to set a precedent that being the food czar is a financial sinkhole.
For more ambitious events, the Food Czar is responsible for determining the requirements of the venue, working with the Sponsorship Czar to determine budget, working with the Lead to find volunteers, ensuring that food details are all on track, and reporting to the Lead on the progress.