I don't know if this has already been linked on this forum, but here is Owain Yeoman talking to John Troy Donovan (Ron) on set. I'm putting it up since it seems some people might like to see it.

Yes, you hear Donovan's voice.  And yes, Yeoman directly asks him: "Is Ron Red John?"

http://www.youtube.com/watch?v=0llrwyH08Sg&NR=1&feature=endscreen

Do with this whatever you will.  (Note: I'm not a big fan of the theory of Ron being Red John, but you never know.)