Workbench access can be restricted through either using the Rhythmyx Server Administrator or by manually modifying the config.xml file located at the Rhythmyx install's rxconfig/Server directory. All changes made by the Server Administrator tool are reflected in the config.xml file.
By default, the product ships so that only those who belong to the Default Community or the Admin role may be able to access the workbench.
The main entry that governs access to the workbench is the "Design access" checkbox, you can add Users, Roles, and Groups to the list.
For example, if I want any user that is in my Artist role to not have access; I would simply add it as a new role ACL.
Attempting to login as the artist1 account of the Artist role results in: