Hi,
I use Ubuntu and I have installed Root version 6.22.00 from a pre-compiled distribution. It works good but I have problems with Roofit, even from the declaration of a variable via RooRealVar: I have written in different ways such as
It is also possible that your pre-compiled distributions has benn built without Roofit support.
Try from the ROOT prompt gSystem->Load("libRooFit")
If it does not work then you need to either build from source with roofit support