In my opinion, women are placed in stereotypical roles. Our Julia character is type-cast as the bimbo or flusey. She sneaks around to get to have relationships with men for purposes of her own pleasure, and then when it comes to thinking about something serious, like a potential rebellion or a moment of joining a conspiratorial revolution, she's not interested.
Of the other women we see, we only receive glimpses. These women are often at work doing domestic chores. I think this further demonstrates the role of women was considered as second-class. Mrs. Parsons spent time being excited about her kids and their futures, Winston can hardly remember his wife or mother, and the woman outside doing laundry was always singing. No woman, besides Julia had significant thought or quality of detail enough for Winston to remember him.
Perhaps the most significant portrayal of women in the novel is represented by Orwell's depiction of Julia, Winston's lover. Julia is first introduced as a somewhat sexless, androgynous figure, and a member of the youthful group the Anti-Sex League. However, as often occurs in the novel, appearances are deceiving (perhaps in response to the backwards logic associated with so many official designations in this dystopian society). Therefore, this anti-sex activist admits she has had sex with hundreds of people! She is also eager to have sex with Winston, and it is the freedom and pleasure they find through having (forbidden) sex with one another that emboldens Winston to join Julia in her efforts to help the revolution.
He says to her, "You're only a rebel from the waist downwards," meaning she is only true to her activist tendencies by being sexually active in direct opposition to her membership in the Anti-Sex League. However, this line (immortalized in the song "Rebel, Rebel" by David Bowie, part of his album Diamond Dogs, which is based upon 1984), encapsulates Julia's significance in the story. Her sexual rebelliousness is a powerful catalyst, both personally for Winston and for herself, but also for the rebel cause she serves and their attempts to overthrow the government. The rules against having recreational sex are a form of control, and sexual freedom is therefore a sign of victory.
It is interesting that Orwell chooses a woman to be the agent of this change, since women's sexuality is so often a source of controversy and repression in society. Julia also rebels against living a life of domestic servitude as someone's wife. She only wants to be with Winston in an autonomous context, and this also opens his eyes to what is possible when one breaks free from government rules and social pressures. His own relationship with his wife Katharine is portrayed as one in which his main memories of her refer to her belief that her main function was to be a wife and mother. Winston's relationship with Julia shows him the wider possibilities that could be available to women in the culture if the current regime were overthrown.