Role in the novel (may contain several spoilers) Edit
As in The Murder of Roger Ackroyd, Christie uses the technique of an unreliable narrator: Michael confesses that he had met Greta many years before Ellie. Since then, they had gotten along and planned Ellie's murder. Nobody knew about the affair between Greta and Michael apart for Andrew Lipincott.
Michael also confesses that it wasn't his first time killing someone; when he was a child he dreamed of having the wristwatch of a friend of his; when his friend fell into water Michael held his head underwater and got the watch.
Mike said that he always quailed in terror when he was around her mother; both Mrs. Rogers and Santonix had understood how dangerous Rogers was. After confessing that he regretted killing Ellie, he strangles Greta because he knew that the idea of Ellie's death was hers.
In the 2013 Agatha Christie's Marple Endless Night episode, he was portrayed by Tom Hughes. In this version, most of Rogers' role remained faithful to the novel, with an additional subplot. When Mike was younger, he apparently attempted to save the brother of Santonix, (renamed Robbie Hayman), but in fact he only snatched the watch of the said brother and left him to die. This happens in the original novel too, but the victim was called Pete and had no connection with Santonix.