Comment # 9 on bug 936979 from Imobach Gonzalez Sosa

So I think that everything is working ok. The behaviour with "ls /root" is the
expected one: the command is executed but there's no output in the GUI. Better
you could try something like:

  xdg-su -c "xterm"

Then you should get an root's xterm.

Anyway, I'm closing this bug as it looks like it's working now. Feel free to
reopen it if you disagree.

Thanks for reporting!