This is my thought about it, if you have not finished both the book series and the films go no further, for there will be spoilers.
Steve said once the film was announced that this was Roland's final go around on the wheel, this is confirmed through Roland possessing the Horn of Eld also, something which he is given in the final book and at the start of his final go around. Roland, in the movie, doesn't seem so much concerned with reaching The Tower, but rather with protecting it, by stopping the evil that The Tower keeps at bay from ever coming into our worlds. The film concludes with Roland defeating Walter, who seemed to be the films villain, and not The Crimson King, and prevents him from tearing The Tower down, which again differs from his book motivation, again another sign that this is the final go around. Roland is able to save Jake, who was the power which was going to destroy The Tower and end Walter in the process, after this is done the whole of Walter's crew, of which Roland has probably murdered, and his base are destroyed. At the end of the movie, again, Roland doesn't seem very concerned with reaching The Tower, he seems content that The Tower is safe and that is all. Roland and Jake decide to leave together, for Jake doesn't have anyone else, what they plan on doing is ambiguous. This was likely set up for another film, but we aren't going to get that, that is why I propose that we have this as the real conclusion. Walter is defeated. The Tower is safe. Roland isn't on the wheel anymore. And that Jake and Roland are content. Besides, it seems that in the final book, Roland had to learn that The Tower wasn't more important than those around him, and he seems to accept this in the film, that he doesn't have to reach The Tower, that he is content with just knowing that it is safe.
Steve said once the film was announced that this was Roland's final go around on the wheel, this is confirmed through Roland possessing the Horn of Eld also, something which he is given in the final book and at the start of his final go around. Roland, in the movie, doesn't seem so much concerned with reaching The Tower, but rather with protecting it, by stopping the evil that The Tower keeps at bay from ever coming into our worlds. The film concludes with Roland defeating Walter, who seemed to be the films villain, and not The Crimson King, and prevents him from tearing The Tower down, which again differs from his book motivation, again another sign that this is the final go around. Roland is able to save Jake, who was the power which was going to destroy The Tower and end Walter in the process, after this is done the whole of Walter's crew, of which Roland has probably murdered, and his base are destroyed. At the end of the movie, again, Roland doesn't seem very concerned with reaching The Tower, he seems content that The Tower is safe and that is all. Roland and Jake decide to leave together, for Jake doesn't have anyone else, what they plan on doing is ambiguous. This was likely set up for another film, but we aren't going to get that, that is why I propose that we have this as the real conclusion. Walter is defeated. The Tower is safe. Roland isn't on the wheel anymore. And that Jake and Roland are content. Besides, it seems that in the final book, Roland had to learn that The Tower wasn't more important than those around him, and he seems to accept this in the film, that he doesn't have to reach The Tower, that he is content with just knowing that it is safe.