The rollback feature is not available via the GUI. At one point (prior to TFS 2010), the rollback functionality used to exist in TFS power tools, but its now in the tf.exe utility.
To use it, open up a Visual Studio command prompt.
Navigate to the folder which maps the TFS folder to your system (the workspace).
Run the following command: (TFS 2010)
tf rollback /changeset:xxxxxx
tf rollback /changeset:from~to