Yes, I have seen Rosabella and I regard it as one of the very best, too. As for Brunnen, really, it does not compete with the Spanish documentary.
Druga strana Wellesa is Croatian, not Hungarian. Among other things, it contains lengthy excerpts from a talk-show on TV Zagreb in the 70ies.
Welles spoke French rather well, as you can hear in another TV show directed by Jacques Rozier (in the series Vive le cinéma !) which includes a conversation between Welles and Jeanne Moreau. So, as far as I know, he alternately spoke French and English on the French part of the shoot of The Immortal Story.
Unfortunately, the Rozier TV show is not commercially available.