Uninstalling TFS 2005 (services) on the app tier removes reporting services virtual directories
After uninstalling TFS 2005 (services) from a standby TFS application tier the SQL Server Reporting Services were not available, i.e. browsing http://server/reports and http://server/reportserver/ resulted in a 404 error.
Workaround:
Run the Reporting Services Configuration Tool and recreate both virtual directories and re-configure the identities.
(Thanks to Daniel Hackel who administers this environment.)