Well, I'd have to say that Electric Fire is my favourite - it's got all kinds of different references in there - Dylan and Springsteen come through very strongly (as you'd imagine).
However, the best album Roger has been involved in outside of Queen has to be Blue Rock - it's absolutely stunning and better than ANYTHING Queen turned out in the 1980's.
It's a huge shame that the success of the Innuendo album gave rise to EMI pulling their financial support of The Cross as I firmly believe that they had a big future.