A straightforward feature that seems to be harder to find each time you need it...
To roll back a change in subversion, you have three basic steps:
- Detect the path to the current folder in the repo:
head .svn/entries - Merge the previous revision back into the current working copy:
svn merge -rCURRENT:OLD REPO_FOLDER_PATH - Commit the new working copy back to the repository.
Reference: Subversion Manual Reference