As is in Hollywood, every decent book is being turned into a movie. Which is a double edge sword. Because every reader wants to see what they imagined projected externally BUT ,and that's a huge but is the other end. Which, regardless of the book, every reader will proclaim to is the story lines in the books are so rich and complicated. To make a comprehensive movie would make it run for hours. (by the way I would love regardless) Hollywood does not have a great track record when it comes to making books into movies. They seem to change the essence of the plot or down play certain characters or scenarios that are the life of the book. To name a few: The Mortal Instruments, both Maze Runner Movies, Dear John, Percy Jackson, the Scarlet Letter, Eat Pray Love and Eragon (DO NOT GET ME STARTED ON ERAGON!!)
So where am I going with this? They have chosen to make one of my top 5 books into a movie. I love Stephen King, I have been a fan of his since I was a child. It was his Bachman Books that roped me in at the age of 8 into reading Horror. But my favorite book is the Gunslinger and the series it is in. King creates a special world that the main character Roland lives in and once you get used to that world King pushes you into another. Testing the readers ability to imagine there are realities and layers to the world we live in. I have always seen Roland as Clint Eastwood or Sam Elliot because of how King wrote the character. These men for me are gunslingers and have the essence of Roland.
Yes they are white and I do agree that we need more diversity in Hollywood. I could actually see Idris Elba be a passable gunslinger if they dressed him appropriately, and the portrayal was done right. For me Roland being white plays into the story line. Especially when he meets other characters of different races. The way he interacts with them is crucial to the development and growth of his character. It is a layer that King put into the plot to make the book deeper. Don't get me wrong, I do not want to see Mathew McConaughey as Roland, that's just blasphemous. To a degree we have to have respect what the Authors have done in their literature. This is someones work of art, a look into their mind and soul; its a labor of love.
So my advice READ THE BOOK always!