You are right in identifying that, although the society of this novel is one that in many ways represents a move backwards towards more traditional, patriarchal values, Rosalind is presented as a strong, self-assured and self-reliant character. However, if you think about her situation, it is easy to understand how she has developed these qualities. Consider her situation: she, like David and the others, is trapped in an elaborate deception in which one false move could result in the loss of her life or worse. Because of this, she has been forced to develop these qualities that you have identified as a matter of survival.
For example, in Chapter 9, we see her resourcefulness and her quick-thinking when she is able to quickly create a fiction to explain her ability to "hear" Petra when she first reveals herself when nobody else is able to:
Rosalind turned an incredulous expression of surprise towards him.
"What! With the way she was yelling! I'd've thought anybody who wasn't deaf would have heard her half-way to Kentak."
Likewise in Chapter 12, when Rosalind, David and Petra flee, it is Rosalind who is the organised and prepared one, showing David to be unprepared and disorganised.
Clearly, then, you are right in suggesting that Rosalind has had to develop certain qualities that show she is resourceful, strong and self-reliant in this excellent dystopian novel.