Creating a new user role with Drush I can do loads of user-related stuff with Drush, but I can't see how to create new user roles. Is it possible to do this with Drush?
This functionality is available in Drush 8.x-6.x:

 role-add-perm (rap)   Grant a specified permission to a role.                  
 role-create (rcrt)    Create a new role.                                       
 role-delete (rdel)    Delete a role.                                           
 role-list (rls)       Display a list of all roles defined on the system.  If a 
                       role name is provided as an argument, then all of the    
                       permissions of that role will be listed.  If a           
                       permission name is provided as an option, then all of    
                       the roles that have been granted that permission will be 
                       listed.                                                  
 role-remove-perm      Remove a specified permission from a role.               
 (rmp)                                                                          


Unfortunately, this has not been backported to the 7.x-5.x branch, so it probably won't be in the soon-to-be-released Drush-5.9, and isn't in Drush-5.8.  For now, you'll have to use the dev branch to get it.