You can have 5 in a room in any room except for a King or a King Suite. We stayed at RPR last June with 5 in our room and it was not a problem. It lets you know on the reservation site how many are allowed per room. Each of us received a room key and we bought wallet lanyards in the gift shop to put them in for easy access.
Oh, and you asked about whether or not they charge for an extra person. I believe that they do charge extra for each adult after the first two, but I'm not sure how much, but if you want to rent a rollaway bed, the charge is an extra $25 per night. I also know that the deluxe rooms at HRH have a sofa bed, so there would be no need for a rollaway.