Great plugin, and works very well with the Capabilities Manager plugin to provide customized user/group/role control.
I noticed that UAM expects the RoleID to be a max of 11 chars long (since INT(11) is the type of the native RoleID in WP). However, if you are using CapMan, you can make your own roles (text names of any length) - so this means UAM will truncate any custom role name longer than 11 characters, and so will not bind that role to the user/group.
Solution is to edit the "object_id" column datatype in table "_uam_accessgroup_to_object" to VAR(50) [or whatever length you want] so that it retains the full custom role name. Looks like a single OTM lookup, so I doubt this will have much of a performance hit.
Hope that helps some people.