What is the particular role of Robert Ross in The Wars?
Your request is very general, so I will give you a very general description of Robert's role.
Robert Ross is the protagonist in this novel about the effects of war on humans. He is used to express the author's theme about mankind's ability to behave morally and compassionately even when tested by the horrors of war. Central to this theme is Robert's one year at the front in 1915-1916 when he was nineteen and twenty. When he enlists, Robert desires to become a war hero, but it doesn't take long for him to lose his beliefs in the glorification of war as he sees horrific events that force him to grow up sooner than he should have. In the end, Robert is driven to committ what some believe is a treasonous act. The author asks the reader to understand Robert's actions, thereby understanding the actions of all who are required to fight in any war.