Rob Reiner was not a character in The Princess Bride. He was the film’s director.
Rob Reiner’s role
Rob Reiner directed and co-produced the 1987 film The Princess Bride rather than appearing as an on-screen character.
The movie’s cast includes Cary Elwes, Robin Wright, Mandy Patinkin, André the Giant, and others in all the major roles, but Rob Reiner’s contribution was behind the camera as the filmmaker shaping the story and performances.