By the end of Act I, we see that Rosalind has a male alter ego, Ganymede, which she uses to accompany Celia into the forest after being exiled and further pursue her own love interest, Orlando. The problem is that Orlando has no clue that Rosalind is underneath Ganymede's guise, and Rosalind has to play both pursuant and confidant to Orlando.
As Orlando hangs poems from trees to catch Rosalind's attention, 'Ganymede' criticises them, warning Orlando that his poetry is not up to the standards it needs to reach. However, when 'Ganymede' realizes that Orlando is the author, the Rosalind/Ganymede dynamic is not as easy to balance. Rosalind realizes that her romantic interest has reciprocated in kind, but has to maintain her guise to stay alive. So, she balances out the male/female dynamic by becoming Orlando's best friend. As Ganymede, Rosalind informs Orlando what he must do in order to further pursue his love. Orlando responds (perhaps too well), and a sense of something beyond camaraderie and friendship develops between Ganymede and Orlando. By the time Rosalind is ready to reveal herself, Orlando does not wish to lose his companion. Lucky for him, Orlando gets the best of both worlds; his love and his favored companion are the same person.
As for Rosalind, her ability to be flexible and adaptive throughout her interactions with Orlando, even as she is in drag, shows her character as one that is more compassionate and understanding - an identity she shares with alter ego Ganymede. When she performed as Ganymede, it is easy to believe that she did not consider the gender norms she was breaking; she believed she was creating a means to an end, and that it would all work itself towards an understanding. However, it is also clear that Rosalind is just as relieved to rid herself of the disguise and show her true gender to Orlando - just as he is relieved that he does not have to lose the companionship he has come to appreciate.