When working with phases in Revit one complaint is that you can’t show rooms from a previous phase.  This is where composite views on sheets works like a charm.  Composite view means more than one view placed on top of each other on a sheet.  Set up a plan view with the phasing set to New Construction and set the Visibility Graphics as desired.  Set up another view with the phasing set to Existing, only display Rooms and Room tags in this view, only tag the existing rooms to be displayed (Note: in Visibility Graphics the Room Tags can be set to Halftone to display similarly to existing phase). Once both of these views are created drag the views onto the desired sheet.  Revit will align the files nicely on the sheets.  The last step is select one of the views, usually the existing room tag view, and change the viewport to one with out a view title.  The room name only view can also be duplicated with dependancies if you need to show the room names on more than one sheet.