What can be understood about the traditional roles of women by examining Ma Joad in The Grapes of Wrath and Catherine in A Farewell to Arms?

In both A Farewell to Arms and The Grapes of Wrath, the traditional roles of men are abandoned by demoralized men; consequently, the women assume the roles of healers and leaders as they adapt to situations, and they break from traditional roles.
In The Grapes of Wrath, once Pa has lost his land, his sense of identity and pride as the provider is taken from him and he becomes impotent. As a result, Ma progressively asserts her leadership; so, while her power does not really increase, it does become more overt in its expression as Pa loses his independence. Thus, Ma is described as being aware of and accepting

her position as healer . . . her position as arbiter. She seemed to know that if she swayed the family shook and if she wavered or despaired the family would fall, the family will to function would be gone. (Chapter 10)

Similarly, in A Farewell to Arms, Catherine emerges as more courageous than Frederic. Frederic tries to be a hero in the war effort by saving people as an ambulance driver, but he fails. Instead, he kills a sergeant and he runs away from the army. He becomes psychologically impotent.

"I'm not brave any more, darling. I'm all broken. They've broken me, I know it now." (Chapter 41)

On the other hand, Catherine is brave and strong; she is, like Steinbeck's Ma, representative of the transforming power of love. Whereas at first she does not believe in the traditional structures of marriage and religion, she later finds meaning and identity in the love she shares with Frederic, claiming he is her "religion." Further, she brings value to both their lives with the transforming power of her love, a love that provides him the strength to continue living after she is lost to him.
Steinbeck's Ma depicts this transforming power of love, as well, as she ensures the survival of the family unit and the continuity of life. For instance, she shares her meager meal for her family with the starving children of the work camp, and she has Rose of Sharon give her dead baby's milk to the weak and ailing man. Ma adapts to situations, and so does Catherine, although in different ways.