Reverting to a previous version with svn (rollback)
To rollback (that is, revert to a previous version) some files/dirs... using subversion, you need as Aral Balkan explains to
Merge the previous version
Like this (assumming you want to roll back from version 61 to 58):
pera $ svn merge r61:58 https://my.project.at.sourceforge/svnroot/project/dir1/src/
[... output ...]
pera $ svn ci -m "Reverted to version 58"
which is strange but works. Forget about the revert command, it has a different functionality.
You may want to run
pera $ svn merge --dry-run r61:58 ........
to check the changes which will take place before messing everything up.