Let's just simplify things and shortlist Christian Bale for every leading man role. Being Batman and John Connor already pushed the needles on the fanboy double-dip meter (the Dark Knight’s fighting Skynet! Tee hee…) but having him be Roland Deschain too would just hike the spikes to the max reading.
The NY Post says that winning the Golden Globe has put Mr. Bale to the front of the Dark Tower's casting race. Most assuredly, he has the steely intensity and the menace-tinged presence the famous Gunslinger needs, but he’s not quite as seasoned as the other actors who’ve been named so far. Roland’s supposed to be a relic from another era, a man more full of regrets and demons than hopes and dreams. And Bale's still pretty much in his prime.
Plus, there’s the bigger question of whether this guy would really even want to take on yet another prospective mulit-film franchise...
The same report gives us the first casting rumors that pertain to other members of Roland’s Ka-Tet, with Ghita Tazi and Jennifer Carpenter supposedly being considered for Susanah Dean. If that's true, I don't think it's too great an idea to be looking for white girls to play the only major minority character in the series. Of course, considering that this is coming from the Post, I'm sure all of this has to be taken with a whole shaker of salt.
UPDATE: Deadline's got the scoop that the role's actually been after Javier Bardem, who I think is a much more appropriate choice. Roland in the looks has a lot of tacit nigh-psychosis that Bardem showed in No Country for Old Men.