Dear Carlo,
The problem is that the linker does not know where the new libraries are.
This is because dlopen searches only in /lib and /usr/lib, so one has to set either the LD_LIBRARY_PATH or to add /usr/local/lib/root to /etc/ld.so.conf and run /sbin/ldconfig again.
I suggest you try the second option: just create a file root.conf with the line /usr/local/lib/root inside; it should look like
$ cat root.conf
/usr/local/lib/rootThen copy the file under /etc/ld.so.conf.d/ with sudo and then run ‘sudo /sbin/ldconfig’.
I agree that the documentation is not completely clear on this point; we will try to improve it.
G. Ganis