Rollback isn't supported in TFS natively. However, it is supported within the Power Tools leveraging the command-line TFPT.exe utility. It's fairly straightforward to revert back to a previous version--with one caveot.
First, download and install the Team Foundation Power Tools 2008 on your workstation. Before proceeding, let's create a workspace dedicated to the rollback. To "true up" the workspace, the rollback operation will peform a Get Latest for every file in your current workspace. This can consume hours (and many GB) with a broad workspace mapping. To work around this, I create a temporary workspace targeted at just the area of source I need to roll back. So let's drill down on our scenario...
I'm working on Program.cs and I accidentally check in a change I shouldn't have. Oops.
Afterwards, select that workspace and perform a Get Latest (just to establish the file system directory). Open up a Visual Studio 2008 command prompt and browse to the workspace on the file system.
To perform a rollback, you can target a changeset or a filespec. I prefer the specificity of the changeset but whatever works for you. You also have flexibility with merge and recursive behavior. Here's the full write-up on MSDN for Rollback. Alternatively, just type in a
TFPT rollback /?
Executing the TFPT rollback command (with the /changeset option in this example), will earn you a prompt to get the latest. Go ahead and click Yes.
Important to note here with the changeset option: you want to identify the changeset one prior to the version you wish to rollback to. So, if I want to rollback to changetset 227, I want to use changeset 228 in the TFPT operation.
Next, you'll receive feedback at the command line about the operation. But wait, you're not finished! Rollback is a local operation. You still need to check in your change. This is a great "safety" if you messed up the rollback itself. Just Undo Pending Changes.
Looking at View History once more, note we actually have a third version and changeset now: 229. But, we've indeed returned to the original (the first, changeset 227) version of the source.
Being back to square one never felt so good...