On previous versions of Server 2012 (i.e. 2008 (r2)) RDS it was possible to shadow your connected users. However with the new release of Server 2012 this feature has been stripped away from the RDS role. The new way of remotely viewing a user session will only be through Remote Assistance. This feature was already shipped with 2008 (r2) but is now the sole way of remotely view assisting your users. You can easilty add the Remote Assistance feature through the Server Manager console or via PoSH of you want to script the installation.