Roles are in essence a set of rights that can be defined per user per site. 

Roles in Castor CDMS have a two-fold purpose:

1. You can easily assign the appropriate rights for a certain user. For example, instead of selecting each right for a user that needs all rights for a site, you can assign them the role 'Admin' - this will select all rights immediately.
2. You can hide a Visit, Form, or Repeating Data structure for a certain user. This is necessary in certain cases where you don't want to show all parts of the eCRF for some users. You can create a role of your own, called, for example, 'Principal Investigator', and you can choose which parts of the eCRF you want to hide for that role.