Creating a new role from the Administer table by cloning an existing role results in no value being entered into the 'builtin' field. This makes the role non selectable in the user and groups menus and not deletable. Work around is to update the roles table directly eg: "update roles set builtin = 0 where id = xx;".

Note: This is 1.11.2 which is not selectable below so please accept my apologies if this has been fixed in 1.11.3