was that Ros was fail-safe for the writing of the plot. You'll recall that Martin was still struggling with the Meereenese Knot when the show started airing. They introduced Ros, and then quickly established her as being extraordinarily well connected for a mere show-created character. She was from the North, knew Theon Greyjoy, met both Lannister brothers, moved to Kings Landing, and got Littlefinger interested. In other words, had the show ever ended up writing itself into the same corner that Martin had been struggling with (since at the time they had no way of knowing how he would write the story out of the knot) they would have on the show a character they could use to introduce other characters who otherwise might not have any connections with each other to each other. A writers failsafe. But Dance was published. Martin got past the plot knot. And Ros it seems was no longer needed. Alas.