The actors never stepped outside a soundstage for ROTS, so far as I know. Even if they did shoot outside, it was still probably on a backlot.
McCallum bragged about how they went to more separate locations around the world for RotS than on any previous Star Wars movie, but these were entirely for purposes of getting live-action effects plates. For example, a crew was sent to Sicily when word got out that Mt. Etna was erupting. They got some footage (from a distance, of course) and used it to help create Mustafar. Some shots from Switzerland were used to realize Alderaan while remote locales in China and Thailand formed the basis for Kashyyyk. The Tunisia plates for the Lars Homestead were filmed while they were there for AotC. I'm not sure if they went back to Italy and/or Spain for that short scene on Naboo.
The locations crews for the various shoots are all listed in the end credits of RotS.