To me Rick is an essential part of Floyd, his backing vocals were a huge part of their sound, as well as his keyboard work. It was a part that was sorely lacking on the latter Floyd albums, which for all intents and purposes were Waters solo albums.
There’s only one Pink Floyd Album with Rick, but not Roger: the Final Cut. Although The Wall was more dominated by Roger than, say, Dark Side, Rick was very much integral, and you can tell by the sound. After the Final Cut, Roger left, and Rick rejoined, unofficially before A Momentary Lapse of Reason, and officially shortly afterward. (He was keyboard throughout Momentary Lapse.)