i know that the usage of the services under WMRoot package is not a solution and SAG do not support this, I would like to understand the usage/functionality of these services.
Do we have any help/documentation for the help on these services which are under wmroot?
I understand your point but unfortunately the documentation on WmRoot package are forbidden to the customers due to several reasons.
And also the source code are hidden and they are used for only internal purpose and not exposed to public. 
For more information on this get in-touch with the SAG team.