A Doll's House does explore concepts of dependence and restricted social roles, but the play looks at dependence as it applies to both male and female perspectives.
Nora is the primary example of a woman constricted by social role as her husband, Torvald, habitually diminishes her intellectual stature and her mental abilities. She is given a defined set of decisions to make in the household and even these are directed by Torvald's opinions and choices.
Despite this gender driven social stricture, or perhaps because of it, Nora strives to define herself as a potent and capable individual very early on. In her conversation with Mrs. Linde, Nora proves her abilities by revealing the fact of the loan she took out with Krogstad.
In this same conversation, Mrs. Krogstad is defined as a woman who is not dependent on anyone and who desires to be needed. She wants to have people to depend on her. This is clearly a break from the notion that women are dependent on their mates. Mrs. Linde futher proves her potency by proposing to Krogstad and also by keeping her new job at the bank.
Torvald is also a figure of dependency in relation to Nora. In much the same way that he has simplified her personality and identity to suit him, Torvald has done the same to himself, relying on generic stereotypes to function as his identity. Nora is critical to this construct and when she announces her departure, Torvald's dependency on Nora as part of his own indentity is exposed.
A major theme in the play is the role of women in the 19th century.
Nora, Torvald's wife, struggles with the fact that she has always had to depend on the men in her life. When she was young, she depended on her father. Now she depends on Torvald. In the first act of the play Torvald calls Nora a spendthrift and other condescending pet names. The fact that she needs to ask her husband for money and the fact that she needs to sneak around when she wants to eat a macaroon illustrates the control Torvald has over Nora. In act three Nora realizes that she is naive to the world. She did not realize that forging a name to borrow money for her sick husband would be considered such a crime. At the end of the play she realizes that she must leave her husband and children behind. She realizes that she has a lot to learn about the world and she wants to be an independent woman.
On the other hand, Mrs. Linde, Nora's friend, is a independent woman. She has lost her husband and she has had to work in the real world. She arrives at the Helmer's house looking for a job. Mrs. Linde acts as a foil to Nora, and she helps Nora see that she needs to experience the world on her own terms. When Nora leaves her home, she plans to stay with Mrs. Linde.
Ibsen probably wrote the play to comment on the limited role of women during the 19th century. There is an alternate ending of the play that changes the entire meaning. In the alternate ending Torvald uses the kids to guilt Nora into staying. You may want to look up the alternate ending.