How many books are in the Stephen King series of which Roland Deschain of Gilead is the protagonist?
eight
Title: The Dark Tower (2017 film)
Passage: The Dark Tower is a 2017 American science fantasy western film directed and co-written by Nikolaj Arcel.  A continuation of Stephen King's novel series of the same name, the film stars Idris Elba as Roland Deschain, a gunslinger on a quest to protect the Dark Tower—a mythical structure which supports all realities—while Matthew McConaughey plays his nemesis, Walter Padick, the Man in Black, and Tom Taylor stars as Jake Chambers, a New York boy who becomes Roland's apprentice.
Title: Roland Deschain
Passage: Roland Deschain of Gilead is a fictional character and the protagonist of Stephen King's "The Dark Tower" series.  He is the son of Steven and Gabrielle Deschain and is descended from a long line of "gunslingers", peacekeepers and diplomats of Roland's society.
Title: The Dark Tower (series)
Passage: The Dark Tower is a series of eight books written by American author Stephen King that incorporates themes from multiple genres, including dark fantasy, science fantasy, horror, and Western.  It describes a "gunslinger" and his quest toward a tower, the nature of which is both physical and metaphorical.  The series, and its use of the Dark Tower, expands upon Stephen King's multiverse and in doing so, links together many of his other novels.  King has described the series as his "magnum opus".  In addition to the eight novels of the series proper that comprise 4,250 pages, many of King's other books relate to the story, introducing concepts and characters that come into play as the series progresses.
The Dark Tower (series) Roland Deschain