Well, here's my opinion. I am a drummer and one of my bands is a tribute band to Queen. :)
To start of, Roger is a very good drummer. He has a great sense of rhythm and specially (and this is very important) he gets the job done. I mean, what he lacks in tecnique, he compensates with creativity and inteligence while drumming. He does not go to "places" where he might do mistakes. These days, his drumming is not so intense like the old days, but he does much less mistakes.
Example: I'm in love with my car. In the 2005/2006 tour, he made much less drum fills that he usually did in the seventies.
Second, mind that not all Queen songs were recorded in the studio with real drums. Their 80's material have few real drums and in their last 3 albuns (Miracle, Innuendo and Made in Heaven) there are a lot of real drums mixed with programmed ones).
Radio Ga Ga has no drums at all.
Innuendo has some real drums, but far much more programmed drums sounds that most of you can think of.
Breakthru. I am almost sure that it also has no real drums.
The speed part in I want it all is all programmed.
Roger was always good in adapting his drum style to the song, never losing his personal touch. One of the things I most admire in him, is that he is a human player, with a good rock feeling.
Now, answering to your questions. Almost all great drumming moments of Queen are in the 70's.
Some moments Live:
Liar (Earls Court 77) I stand in awe everytime I see this.
Some solos in Keep Yourself Alive (specially when he did the samba-like groove with the cowbell, in 1976-78)
Some of the Best Studio moments:
Great King Rat finale
March of the Black Queen
Death on 2 Legs
Hardest Queen Song to Play on the Drums?
Now I'm Here? NO! Seems hard, but it's easy.
The answer is...
... The Loser In The End.
(Genious work by Roger... oh and John's bass is equally divine. Just raise the volume in the end of the song)
Being a Scolar when it comes to Queen...