Who is the traitor? (Game of Thrones: A Telltale Games Series)

So who is the traitor?
There are several suspects Maester Ortengrin, Duncan Tuttle, Ser Roiland
I think in episode 5 we find out who the traitor is as it is shown how Rodrik reads the letter and says "How could I trust him" although he may be talking about Ludd Whitehill who took Griff and kept him or killed Rayon (although Gwyn would have kept her father from such an act).
Let's start with Ser Roiland. I don't know how he can be suspected he hates the Whitehills with all his heart. Although this is probably just a cover and in my case it could have been pushed by the fact that I chose Duncan as a guardian.
Now Duncan, here's more evidence of his guilt.
For example, when we meet with Gwyn, Whitehill riders immediately appear from where they learned about the meeting. Although he could immediately tell that Gwyn was reporting to Rodrik about everything.
Secondly, he could tell the Whitehills about the northern grove, and they in turn sent Britt to the wall in order to find her.
Although he is the uncle of one of the protagonists, this does not change anything.
He's also nice to the Whitehills all the time.
Well, I don't want to write about the maester. :-)
Write what you think about the traitor.