Not a continuation of the recent movie that bombed--the series will be a prequel that focuses on Roland as a young man. Sam Strike has been cast as Roland, while Jasper Pääkkönen will play the Man in Black/Randall Flagg. Jerome Flynn (Bronn in GOT) has also been cast but no word on the character he'll play.
No date yet for when the series will premiere, but it sounds like it'll start filming soon.