You can try downloading the previous revision from TeamServer, and then commiting it with a small change. This will make it the newest revision in your main line.
I don't think you can deelte a revision from TS.
You can not delete a revisoin from SVN, you can just revert it. The "Team"->"Reverse merge changes.." button states this explicitly.
Under Team you have the option to reverse merge changes.
With this option you can revert commits. Here you can select one or more commits to the teamserver and revert those changes.
I likek to use a tool like TortiseSVN to manage my repository on my local machine. Using this tool, you can revert changes to any revision on the team server. The version that works is 1.7.X as outlined here:
Here is a link to the most recent 1.7 version.
This tool will help you solve this problem and I have found it very useful to resolve merged changes that occur in files outside of the modeler (theme, java, etc)