Updating to new roofit versions


I know this is an extremely naive question, but it is one I need answered. How does one update to newer versions of Roofit? I’ve tried building new root versions from source, but I keep running out of disk space (I am running from an lxplus machine). I’ve also tried

cd /afs/cern.ch/sw/lcg/app/relcd /afs/cern.ch/sw/lcg/app/releases/ROOT/5.30.06/i686-slc5-gcc43-opt/root . /afs/cern.ch/sw/lcg/external. /afs/cern.ch/sw/lcg/external/gcc/4.3.3/i686-slc5-gcc43-opt/setup.sh . /afs/cern.ch/sw/lcg/app/rele. /afs/cern.ch/sw/lcg/app/releases/ROOT/5.30.06/i686-slc5-gcc43-opt/root/bin/thisroot.sh

which allows me to run with newer versions (most of the time), but when starting a root session I get the error

Error in <TUnixSystem::Load>: version mismatch, /afs/cern.ch/atlas/software/releases/17.0.3/GAUDI/v22r1p4/InstallArea/i686-slc5-gcc43-opt/lib/libGaudiPythonDict.so = 52800, ROOT = 53006 Error in <TCint::AutoLoadCallback>: failure loading library libGaudiPythonDict for class basic_ostream<char,char_traits<char> >

so what is the proper way to use updated versions of Roofit?