The Dark Tower with....

[MatthewMonster]

JJ Abrams at the helm ?

http://www.aintitcool.com/node/31580

[RandallFlagg]

So, who do you cast? I've been thinking about this for quite awhile.

Roland: Viggo Mortenson. I'm sort of hesitant about this, but I still think this works.
Eddie: Jared Leto. He has the look, he can play a drug addict very well, and I think he's just a damn fine actor.
Susanahh: Thandie Newton. Her performance in Crash was superb.
Randall Flagg: Val Kilmer or Nathan Fillion.
The Crimson King: Donald Sutherland
Jake: You need a good child actor. Not sure who.
As for the others, I'm not really sure. I covered the main bases.

[Aaron Wilder]

Roland: Gabriel Bryne
Eddie: Milo Ventimiglia (Peter Petrelli)
Susannah: Rosario Dawson (Clerks II)
Jake: Cameron Bright (Leech from X-Men 3), the picture in Wikipedia looks exactly how I picture Jake
Flagg: Johnny Depp, hands down
Crimson King: Donald Sutherland is an awesome choice
young Stephen King: writer Joe Hill (his son)
Father Callahan: Christoper Walken

[RandallFlagg]

Crap! I totally forgot about Father Callahan! My choice has always been Clint Eastwood. He is totally perfect for it. But barring him, I do like Christopher Walken, but I was also thinking maybe Tommy Lee Jones.

[BobRivard]

Man, I really hope this idea comes to fruition. And if it does, it's handled properly. I've always wanted to see this as a movie.

I think all the casting choices you guys listed would all work. Viggo as Roland could work... he's got the look, but I don't know if he'd be able to handle that character (at least from what I've seen of him). Johnny Depp would be good as Flagg, but I always thought he'd be great for Roland.