If you want to restrict the grouping to the parent 'item' element then
one way to do that is to integrate the generated id of the 'item'
element into the key, as in the following stylesheet:

     <xsl:key name="role" match="planItemOrganization"
use="concat(generate-id(parent::item), '|', role/name/name)"/>

Great! I attempted to solve this, but then realized that vanilla
Muenchian grouping won't work here, so I gave up, trusting that one
of the usual suspects would pick up the task. Thanks for this nice
solution!