Roslin Tully

Roslin Tully, née Frey, is the daughter of Walder Frey and wife to Edmure Tully who is first seen in Season 3. She was previously the intended bride for Robb Stark.

Background
Roslin is the 19-year-old daughter of Lord Walder Frey, Lord of the Crossing. Unlike the majority of Lord Walder's brood, Roslin is quite beautiful. She was intended to marry King Robb Stark as part of an alliance between her father and him (Walder had given Robb a choice of any one of his many daughters or granddaughters, but Roslin would have been the obvious choice), but Robb fell in love with and married Talisa Maegyr instead.

Season 3
"Black Walder" and Lothar Frey arrive at Riverrun after Robb Stark offers to renew their alliance, but Black Walder relays that Lord Walder insists that Edmure Tully must immediately marry Roslin, having "gone off" long engagements after Robb reneged on his engagement. Edmure initially refuses, but eventually consents after bowing to family pressure as well as his desire to make amends for his blunder at the Battle of Stone Mill.

Edmure does not meet Roslin until she is unveiled at the wedding. Having seen Walder's other daughters, Edmure was shocked and relieved to see Roslin at last. The newlyweds got along quite well until Robb and Walder called for the bedding ceremony, when Roslin was carried off by Frey and Tully attendants to the bridal chamber. It is not known what, if any, involvement Roslin had in the planning or execution of the grislier parts of her wedding.

In the books
In the A Song of Ice and Fire novels, Roslin is born from Lord Walder's sixth wife, Bethany Rosby. Roslin is the fifth child that Bethany bore Walder, and she has four older brothers: Perwyn, Benfrey, Willamen, and Olyvar. Members of House Rosby are known to have frail health to begin with, and Bethany's frequent pregnancies took a heavy toll on her body. Walder kept Bethany almost constantly pregnant, having a new child every year of their marriage, and ultimately Roslin's mother died not long after she was born.

Roslin is described as being the prettiest of Walder Frey's offspring. She is small with very white skin, a pretty face with a small chin, delicate nose, and big brown eyes. Between her teeth she has a small gap. Her hair is brown and reaches her waist. She has a gentle nature and a talent for music. Roslin was seventeen years old in the third novel, but in the corresponding section of Season 3 in the episode "The Climb", she is stated to be nineteen years old: this is in keeping with how most of the younger cast members have been aged-up by two years in the TV continuity.

Unlike in the TV series, Roslin is introduced to Edmure shortly after he and the Starks arrive at the Twins. Since she is so small and has narrow hips, Edmure and Catelyn are concerned about her fertility. Catelyn discusses it with Maester Brenett, and he assures her there is nothing to worry about, for Roslin's mother gave Lord Walder a child every year, five of them have lived past infancy.

Edmure finds it strange that Roslin is sobbing when she meets him. She tells him "I weep for joy, my lord". Only a moment before the massacre begins, Catelyn realizes the real reason for her tears: Roslin knew about the scheme and was forced to go along.