Rosalie Lillian Hale was born to a middle-class family in 1915. When she was 18, the Great Depression hit the US. Her father had a stable job in a bank. Her parents were social climbers. Rosalie, who was extraordinarily beautiful, was the ticket they needed to reach their social aspiration. She was clearly the favorite of her parents, with two younger brothers.
Meanwhile, Rosalie dreamed of a lavish life--a life with a rich husband and children as beautiful as she was. Her parents influenced her want of material things. She wanted a big house that someone else would clean, with a large lawn that she would play with her children on.
In Rochester, where she grew up, there was only one family that had what her parents wanted--the Kings. Royce King owned the bank Rosalie's father worked in. His son, Royce II, and Rosalie began dating. The engagement went quickly too and wedding plans were made. Rosalie couldnt help but feel something was missing from her relationship with him. She soon began wanting what her good friend, Vera, had-- a husband who wasn't necessarily rich, but one that loved her and was there for her, and a small baby they could raise together lovingly.
One night she went to Vera's, and while walking home she realized how late it was and she wished that she had thought to call her father to escort her. On the way, she saw several drunken men. One turned out be Royce. Showing her off to his friends, he ripped pins from her hair. When she cried out in pain, the men seemed to enjoy it. They proceeded to beat and then rape her.
Afterwards, they left her dying in the street. Carlisle Cullen found her. Rosalie had never liked Dr. Cullen or his wife and her brother, as Edward then pretended to be. It bothered her that the family was more beautiful then she was. Dr. Cullen, who turned out to be a vampire, saved Rosalie that night by turning her into a vampire. The "vegetarian" family only drank the blood of animals. Soon after becoming a vampire she killed Royce and his friends--careful not to spill a drop of blood. Since then, Rosalie prides herself on never having drunk human blood.
Two years later, she found Emmett being mauled by a bear and ran him back to Carlisle. She begged for him to save the dying Emmett, who reminded her of Vera's little boy, by changing him into a vampire. The two were soon married. Rosalie and Emmett currently reside in Forks, Washington, but they often live away from the family as a married couple. Currently she is the only one, aside Carlisle that has kept her last name on the grounds that she never wanted to be a vampire in the first place.
In New Moon, she mistakenly reports to Edward that Bella is dead after she supposedly commits suicide, though Bella was actually just partaking in the sport of cliff-diving. He then proceeds to travel to Italy, desiring to have the Volturi kill him, only to be stopped by Alice and Bella. While most of the Cullens votes in favor of changing Bella into a vampire, Edward and Rosalie vote against it changing her.
In Eclipse, Rosalie reveals her past to Bella with the hopes that she will choose to stay a human being. She also joins the fight against a group of savage newborn vampires.
In Breaking Dawn, Bella learns about her pregnancy and Edward is afriad that the baby is killing her with it's accelerated growth that he orders her to get an abortion to save her life. She refuses, knowing she has a connection with the baby and contacts Rosalie for support, knowing that she has always wanted to have children. She stays by Bella's side throughout the pregnancy, and defends her choice to keep the baby, causing Edward to reconsider forcing his wife to get an abortion. Rosalie acts as a guardian to the child, Renesmee, taking care of her while Bella is going through her painful transformation into a vampire and they become very close. When the Volturi plot to destroy Renesmee, Rosalie helps gather vampire nomads, with Emmett, to provide evidence that Renesmee isn't a danger to them.
Rosalie is described as tall, statuesque and blonde. She's vain and self-centered on the outside. However, the truth is that she longs to be human and have children, so much that she's willing give up her immortality, beauty and even Emmett for it. It's for that reason she strongly resents Bella Swan with a passion. Rosalie knows that she's being foolish in wanting to throw away her humanity just to be a vampire, which Rose herself never wanted to lose in the first place.