Ros is a prostitute of renowned beauty. Originally working in a brothel at Winterfell, on the eve of the outbreak of the War of the Five Kings Ros relocates to the capital city of King's Landing, where she finds employment at the high-class brothel of Petyr "Littlefinger" Baelish. She later spies on Littlefinger in exchange for Varys ' promise of protection, but Littlefinger somehow finds out about their deal and she dies after he gives her to King Joffrey to use as a live target for his crossbow, and she is killed by multiple crossbow bolts while tied to his bed.
Ros is a prostitute in a brothel in Winterfell's outlying town. She has drawn the attention of the young nobles of Winterfell including Theon Greyjoy and Jon Snow. Theon is a regular customer while Jon is not. Jon once paid Ros for her time but did not have sex with her because of a pang of conscience over the possibility of fathering a bastard when he has suffered the life of being a bastard himself.
Ros says that she grew up in the town outside the walls of Winterfell, and remembers the day Sansa Stark was born and all the bells of the castle were rung in celebration (thirteen years before the beginning of the TV series). Ros is literate, which is uncommon for most prostitutes.
Ros is shown entertaining Tyrion Lannister shortly after his arrival at Winterfell. She informs Tyrion that the whorehouse was especially alerted to his imminent arrival, though by whom is not revealed.When Tyrion is returning from the Wall, he stops at Winterfell. Believing the Lannisters are responsible for Bran's fall, Robb denies him Winterfell's hospitality. When Tyrion is leaving to go stay in town, Theon Greyjoy recommends Ros to Tyrion, unaware that Tyrion is already acquainted with her. Tyrion promises "not to wear her out". At Castle Black, Jon Snow and his friend Samwell Tarly talk about having never been with a woman. Jon says that he once had the opportunity to have sex with a young and gorgeous whore named Ros. He describes her to Sam with red hair and indescribably perfect breasts. Jon ultimately declined to have sex with Ros, due to his fear that if he fathered bastard children of his own, as a bastard himself he would have nothing to offer them. Theon sneaks Ros into his chambers, were they both undress and have sex. He notices that she is wearing a Lannister lion pendant and she tells him that it was a gift from Tyrion. He becomes angry when she insinuates that Tyrion is a superior lover and that his family's honor is suspect due to the failed Greyjoy Rebellion. When he refuses to pay for the encounter, Ros suggests that he gets a wife instead, infuriating Theon further.
Theon is surprised to see Ros sitting in the back of a turnip cart. She tells him she has decided to leave Winterfell to seek out employment in King's Landing, and is planning to get a ship from White Harbor. He unsuccessfully tries to persuade her to stay, but she points out that, with war coming, all the men will be marching away and there is nothing for her here. Theon throws her a coin, and she laughs and lifts up her skirt one last time. Theon reluctantly says he'll miss her, and she agrees that he will.
Arriving in King's Landing, Ros finds employment at a brothel owned by Littlefinger. He tutors her and another prostitute, Armeca, in the art of seduction. Ros learns that Littlefinger is infatuated with a woman who was betrothed to a man who injured him in a duel, but she later married the man's brother. However, it does not appear that she recognizes the woman in the story as Lady Catelyn Stark
Ros's services are employed by Grand Maester Pycelle in King's Landing. As she gathers her clothes to leave, Pycelle begins to tell her about all the kings he has served, eventually his ramblings fade and she becomes impatient, questioning him about the original point of his speech. She leaves, frustrated.
Ros watches two new prostitutes in Petyr Baelish's brothel practicing their work. She repeats Petyr’s advice to ease into the act slowly and with passion. She tells the new employees to wash and dress for work that night before walking away. She is followed by Daisy, who she instructs in the merits of their upmarket brothel. She greets Lord Orson who is passing with a young man as she tells Daisy that they cater to a higher class of customer than she was used to in Haystack Hall. Daisy watches Armeca leading a client away. Ros notes that Armeca pretends not to speak the Common tongue in order to seem exotic and reveals that she actually grew up in Flea Bottom. Daisy says that Armeca is beautiful, but Ros is dismissive of her colleague.
Lord Commander Janos Slynt enters with several of his men. Ros greets him with familiarity. More goldcloaks enter with a bloodied prisoner and Janos snaps his fingers at his men who begin to search the brothel. Ros reminds him that Petyr is the establishment’s owner and Janos cites orders. Ros wonders who the orders came from and Janos tells her only that they are from someone who doesn’t care what Petyr thinks. Mhaegen is dragged into the room, holding her baby Barra (one of Robert’s bastards). Janos looks at his prisoner who nods recognition. Janos then signals one of his men who takes the baby from the sobbing Mhaegen, draws his knife and then hesitates. Janos tells his man to kill the baby and then does it himself when his subordinate cannot, horrifying both Ros and Mhaegen.
Ros is still visibly upset about the death of Barra. She is so distraught that she falls apart in front of a client. Lord Petyr Baelish comes into her room and she confides in him. However, Baelish compares her to a beautiful girl he purchased from a Lyseni pleasure house for an exorbitant price. The girl was so sad Baelish gained no money from her and he sold her to a Lord who wanted to "transform" her, a man who derived pleasure from things most men would find unthinkable. After this lesson, when he asks Ros if one day off will make her smile again Ros smiles and assures him it will.
Tyrion Lannister, on the suggestion of Bronn, hires Ros and Daisy as a nameday present for his nephew King Joffrey Baratheon. Tyrion hopes this will give the sadistic Joffrey an opportunity to release his frustrations away from Sansa. They wait for him in his chamber. When he arrives Ros wishes him a happy nameday and then reaches for his crotch. He flinches and then instructs Ros to touch Daisy. He asks if Ros can hit Daisy and she spanks her gently. Joffrey asks if Tyrion sent them and Ros says that Tyrion chose them himself. Joffrey takes off his belt and gives it to Ros to use. He forces Ros to hit Daisy hard enough to make her scream. He hands Ros a stag’s head sceptre and she protests that too much pain will spoil the pleasure. He loads his crossbow as Ros warns him that his uncle might find out. He tells Ros that he wants Tyrion to find out and orders her to take Daisy to Tyrion’s chambers to show him what has happened or she will also be beaten. He aims the crossbow at Ros and orders her to begin, as Daisy screams.
Ros is captured by Queen Regent Cersei Lannister, who mistakenly believes that she is Tyrion's lover (as a result of the Lannister pendant Tyrion gave Ros in Winterfell). She has Ros beaten and kept prisoner. She plans to use her captivity to force Tyrion into keeping Joffrey safe, believing that Tyrion is plotting to kill him. When Cersei says that she has his whore, Tyrion - thinking she has the dark-haired Shae - remarks that he thought she preferred blondes, but it is red-haired Ros that she has brought in and displayed beaten to him. Cersei explains that she will kill her in the most gruesome way, if harm comes to Joffrey while he mans the city walls, as Tyrion plans. Tyrion plays along to maintain the secret that Shae is his true lover; Ros does the same. Tyrion vows to free Ros and she begs him not to forget her.
Some time after the Battle of Blackwater Bay Ros was freed, and is then visited by Varys, though she doesn't realize who he is until she discovers his eunuch status. Varys gets Ros to admit she's afraid of Littlefinger, and tells her that unlike her current employer, he protects those who work for him.
Ros accompanies Littlefinger to the docks, where he has a quiet word with Sansa Stark. Left alone with Shae, Ros explains that she helps Littlefinger manage his affairs. She also tells Shae of the day Sansa was born, when all the bells in Winterfell were rung in celebration. Ros asks Shae to watch out for Sansa. When the Lorathi responds that she always does, Ros clarifies that she is referring specifically to Baelish.
Following Tyrion's appointment as the new Master of Coin, Ros assists him and Littlefinger in retrieving the Iron Throne's financial records from their hiding place under the floor of the brothel's office. Ros titillates Podrick Payne during the exchange, apparently for her own amusement.
Ros is revealed to be meeting regularly with Varys to report on Littlefinger. She updates a slightly incredulous Varys on Podrick's apparently prodigious sexual skills, which she has had trouble verifying as the usually descriptive prostitutes he slept with seem to have been rendered speechless. When Varys asks how Littlefinger reacted, Ros says he didn't even notice and expresses concern about his plans for Lady Sansa. She presents Varys with a shipping manifest for Littlefinger's upcoming journey to the Vale. Surprising the Spider with the revelation that she is literate, Ros points out that Littlefinger has requisitioned two feather beds for his cabin - he is planning on taking someone important with him: Sansa.
When Littlefinger finds out she is spying on him for Varys, he gives her to King Joffrey, who wanted to try something "new and daring". Joffrey used Ros as a live target, brutally killing her by shooting her and pinning her to his bed with multiple crossbow bolts.
A prostitute from the North who journeyed to King's Landing, Ros helped Littlefinger run his brothel. When Littlefinger discovered she was a spy for Varys, he offered her to Joffrey to satisfy the king's bloodlust. Joffrey killed her with his crossbow.