Unlike Ben, Rook is more stoic and prefers to think before acting. He used to treat Ben more like a superior instead of a friend/partner as he usually addressed him as 'sir' when they first met He now tends to see Ben as a lesser or equal being such as saying he always has to save Ben and that, "[Ben] wouldn't even be alive without [Rook's] help." Although, Ben still manages to impress him from time to time. While he is very intelligent, his lack of experience can make him somewhat naive and often the rear of Ben's jokes. He seems to dislike chili fries. Nowadays, he sees Ben as a friend. Rook still has difficulty understanding his Earthly expressions, and he says that he still can hardly deal with 16-year old Ben. However, in Many Happy Returns, when Ben says that he doesn't always get Rook, but finds him to be cool, Rook explains that the feeling is mutual.
Rook is shown to be formal, such as initially calling Ben "sir" or referring to Gwen as "Miss Tennyson." When Rook first met Ben in The More Things Change: Part 1, he was respectful of him, and in The Frogs of War Part 2, Kevin exasperatingly points out that he's "so polite."