<p>I have a revision that has been committed to SVN trunk which I would like to roll back.  However, I would like to retain the changes in some fashion such as a branch or even a patch file.  Any suggestions?</p>

Reverse-merge (I think that was the term), commit and that's all.
For the "reverse-merge" part - TSVN has this cool feature called "Revert to this revision" (and "Revert changes from this revision"), accessible through the Log dialogue.
The main purpose of a VCS is to keep history of your changes. You could always go back to this particular revision by using "Update to revision..." or by using the aforementioned "shortcuts".