This Report will help you in identifying the collection that are member of any other parent collection.
SELECT
COL.CollectionID,
COL.Name,
COL.Comment,
CTSC.parentCollectionID
FROM
dbo.v_Collection COL,
dbo.v_CollectToSubCollect CTSC
WHERE
CTSC.subCollectionID = COL.CollectionID
The above report is to get collection with its parent collection but if you want to know the root map of particular, go with this post http://blogs.catapultsystems.com/mdowst/archive/2012/02/23/finding-sccm-sub-collections.aspx
