This can't be done automatically.
Here are a couple of workarounds...
1. From release 2009 and on you can do the following:
Settings-Area and Volume Computations-Calculate Volumes
Make sure the Room object is bounded to the ceiling.
Add a Calculated Value to the Room Schedule using the following info:
Name: Ceiling Height, Type: Length, Formula: Volume/Area
Please note that this workaround only works where the Room and Ceiling are the same shape. The ceiling must be flat.
2. Pre 2009, ie.2008 has another workflow. You may even choose do this in all releases because of the complications of the workaround mentioned above.
Make a Shared Parameter called Ceiling Height
Apply this to the Room Object in the Project file as well as the Room Tag
Make a duplicate of your ceiling plan.
Tag all ceilings showing Height Offset from Level
Tag all Rooms
Now that you can see the actual ceiling height you will be able to manually update the Shared Parameter 'ceiling height' in the Room Tags.
This will keep a coordinated Room Schedule, Tags with the ceiling height.