Can anyone tell me how to revert (roll back) a checkin in TFS 2010?
There is no undo option in TFS (up untill 2008, I haven't used 2010 yet). There are some command line power tools you can use to rollback changes that may help:
http://msdn.microsoft.com/en-us/library/ms194956%28VS.80%29.aspx
HTH