Roger Moore, or as he is known in GH circles, 'REM', contributed quite a significant amount of work and effort to the Greyhawk setting as is evidenced in many of his works in 'The Best of AOL' (Greyhawk used to have an AOL folder where lots of fans contributed work, Greytalk and Canonfire are, as I understand it, the offshoots of it) files.
He was somewhat involved in the setup of Living Greyhawk, as I understand it, although Erik Mona would be far better qualified to comment on that. I know that he contributed to the 'Classics' download section for Greyhawk, including the History of the Greyhawk Wars from the Greyhawk Wars Boxed Set.
I know also that he was the Editor of the Living Greyhawk Gazetteer. I think he contributed to the Living Greyhawk Journal in Dragon, or an article or two in Dragon, but I can't remember. Again, Erik Mona is the best qualified to answer that question.