The AOTC and ROTS camera "negatives" (the tapes, anyway) are 1080p. The ROTS model I didn't think improved the resolution, it just gave perks like uncompressed color space and user-oriented upgrades, though I could be wrong. So whatever the "master" of AOTC and ROTS is, resolution wise it is still just your standard HD. I have no idea what the master is, but especially at that time it was standard practice to do your FX at the same res as the camera, and I can't see why this should be an exception--possibly they were done at 2K res, but the difference is so negligable anyway, in any case many of them are integrated into 1080p resolution live-action plates.
It's kind of sad how the Star Wars saga has been perpetually downgrading in image quality--you'd think things would be improving with technology!
1977-1983 OT: Full 35mm anamorphic resolution --wOOt
1997 SE: Partial 35mm anamorphic resolution, with partial 2K res for anything with a special effect or new element in it --its not so bad, par for the course for the 1990s
1999 TPM: 2K resolution scan from 35mm anamorphic original --shame, but at least it came from film in the first place
2002 AOTC: primitive 1080p HD original --low-quality res of low-quality image
2004 SE V2: 1080p scan of 35mm original for home video use --wow, so now Star Wars can never be shown theatrically in a competetive quality
2005 ROTS: slightly less primitive 1080p HD original --is this really worth considering an "upgrade"?