They'll probably always need some human around for liability reasons. That is unless the robot bartender is going to add some sort of breathalyzer component to see if people have had too much.

Also unless it's a club it likely would need to scan the person's ID and confirm whether or not the person was who the ID mentioned adding some complexity to the robot that otherwise wouldn't be required for just serving drinks.

The sysadmin person you mentioned could definitely take on that liability role in addition to anything else he needs to do to support the robot.