There's a Varric/Blackwall banter in Inquisition that is probably my favourite quote to come out of the dragon age series and also says so much about Varric and also about Hawke but reframed in the context of Veilguard also says so much about Rook and why those people complaining about Rook 'not being a main character' or Rook 'not having any right to be the leader' are so completely missing the point of Rook.
Blackwall: You can't really think Reeve Asa is a better knight than Honorine Chastain. Her record's flawless. Four hundred jousts, never unseated. No one's ever come close to it.
Varric: Oh, she's easily the most skilled, that's a fact. It's just that 'scrappy' is better than 'flawless'. I like heroes who try their damndest, even if they fail a lot. It's easy to be valiant when you always win and everything goes your way. There's nothing great in that.
In Inquisition, obviously Varric is talking about Hawke. Hawke, the tragically doomed hero who tried and failed to save Kirkwall, but who tried. Now explain to me why Varric would pick anyone other than Rook to be his second? To look after the team while he talks to Solas? Varric is, first and foremost, however much he tries to be something else or pretend he isn't, an idealist. An author. He lives and thinks in terms of stories, it helps him deal with and make sense of the world. So why would he go and try and recruit the type of hero he doesn't like? Yeah, Rook is a nobody. They're probbaly not the best at what they do and the only reason Varric notices them is because they get cast out of their organisation for going against orders to save people. They might not be the most skilled, but goddamn if they don't try. Rook is the definition of scrappy, the prologue and first couple of cutscenes basically hit you over the head with it multiple times. They're exactly the stuff heroes are made of, according to Varric. And sure, they need some help, but what good would a story be if the hero was perfect all the time?
God I love Rook. And I love Varric and the way he thinks. And you know what? You know what the game says?