To unassign roles from a specific user, click on "Users Management" from main menu and search for the platform user.
Select the user by checking the box next to the name and click on "Unassign roles". From the window that will then appear, select the role you wish to unassign from the selected user and click on "Save" to confirm. A message confirming that the action has been successfully performed will display.
Please note that if a user was only assigned the role which has now been unassigned, at the first log in the user will read an error message explaining that there is NO domain in the system assigned and therefore it is not possible to login to any domain.