The role play scenario is key. You really can't prepare as there is no time to prepare. Just don't get flustered and ask questions. They are trying to see if you crack under pressure. I made two big process mistakes (writing a check to a customer was one of them) and still passed. The people part of it I handled well, not perfect but well. They clearly know how to pick out what they are looking for by almost this alone. If they like you and you fail this miserably you are out. Keep cool and don't take anything personal. That is the key thing in a job like this.