Assume that revision 92 contains the changes we are undoing.
In order to undo a commit that has been made to the repository we just tell SVN to apply the reverse of the changeset to our working copy in the current directory.
svn merge --revision 92:91 .
The output will show files being updated or deleted, we can now check those changes.
And if all looks good we can commit our repaired files.
svn commit -m "removing changes from revision 92"
Good to go!