Hi,
the “trunk” version is always the latest, but since it is work in progress (i.e. it isn’t yet released) it is not always the greatest yet (otherwise why wouldn’t it be released). You should instead use some release instead, e.g. the latest which is 5.34.03. If you insist on svn use
$ svn co http://root.cern.ch/svn/root/tags/v5-34-03but this should pretty much give you the same as downloading the tarball from the ROOT homepage (ftp://root.cern.ch/root/root_v5.34.03.source.tar.gz).