Ross serves as an observer in Macbeth; he was previously used in Act One, scene two to tell of the final events when Macbeth defeated the original Thane of Cawdor. In Act two, scene four, Ross once again takes on the role of observer and comments on the strange happenings in the castle.
MacDuff is a much more active character. He responds strongly to Ross's casual question of "how goes the world" with "Why, see you not?" In this scene MacDuff not only observes the ill omens, but also chooses to react to them by not attending Macbeth's coronation.