In Team Explorer (in Visual Studio): Tools | Options | Source Control | Visual Studio Team Foundation Server and select Show Deleted Items...
Then in source control explorer you'll see the items greyed out. You can right click on them and Undelete. (This option will only be available if they, after the undelete, will be included in your current workspace).
NB. in newer versions of Visual Studio (eg. 2013) there is now a button to switch on display of deleted items in the Source Control Explorer's toolbar. Its the second button (here with the VS dark theme):

Alternatively using the TFS PowerToys you can look at history and right click to select "Rollback Entire Changeset": this will create pending changes to revert the changes of the selected changeset.
Edit: Added paragraph on newer versions of VS.