One of the annoyances I have found with the Contribute Client is that in the Administration interface section, when adding a user, the menu of roles is not sorted for you. The list that appears when you reassign a user or when you create a new role, is sorted for you.
Each time that a new role is added, the client updates the hub file, adding the new role to the end of the list.
In investigating this I found that the hub file is just an XML file. This file is stored in the root _mm folder of the website that you are managing. Note that this file is connection specific, so if you are managing multiple websites, the location of this control file will vary. And if you are managing a large deployment by having multiple sites with a single directory structure, you will have a different _mm folder and hub file for each site, even though they are physically on the same server they are treated differently by the logic of the software.