Are you implying that someone can't be stuffy with curly hair and a beard. Trust me, people can.
Though I wouldn't necessarily say that Roger is stuffy because that tends to imply dullness, staleness, and humorlessness - and Roger is rarely dull or stale and, as you rightly point out, he has a biting sense of humor with which he tends to skewer almost everyone and everything around him.
Maybe the term we're looking for is conservative. But sometimes conservativeness is more a state of mind than it is an appearance as I'm often surprised that people who look like they wouldn't have a conservative thought in their heads turn out to be ultraconservative.
So even if Roger were to look like Sheen does in the interview, underneath it all Roger could still be very similar to the Roger we know and love.
But be that as it may, I have to confess that I'm not going to fully believe that Sheen isn't in the Depp/DS film until we received confirmation that someone else has been cast in the role of Roger. Although, nowhere was it actually said with certainty that Sheen would play Roger. It was all speculation on the parts of the sites that reported Sheen's interest in reading the script. What is interesting, though, is that as recently as April 4th, when Sheen appeared on BBC Radio 2's Drivetime show, he supposedly indicated (as per collinwood.net's DS News blog) that he would be appearing in the film. Go figure...