In context of this saying, "Shakespeare has no heroes, but only heroines," what are the leading traits of Rosalind in As You Like It.
Shakespeare is said to not have heroes in his comedies because of the significant role the lead female characters play (this may not be as easily asserted for his tragedies and histories, however). Critical opinion holds that in his comedies, one thing Shakespeare aimed for was to honor the qualities of Queen Elizabeth. Other Elizabethan Renaissance writers similarly honored Elizabeth in their writings, most notably Edmund Spenser in The Faerie Queene. Since Shakespeare aims to honor Elizabeth, he endows his heroines, such as Rosalind in As You Like It, with qualities and attributes widely know to belong to the Queen. One reason writers wished to honor Queen Elizabeth, aside from the privileges of patronage (e.g., court positions or pensions), was that Elizabeth was lauded in her own time as one of England's greatest rulers, who, though a woman, was fearless even in the face of battle as she was noted for donning armor and riding at the head of troops.
The characteristics of Rosalind show her with both expected female virtues and weaknesses and with characteristics that transcend gender expectations, likening her to Elizabeth. Some of Rosalind's key feminine qualities are compassion and tenderness as illustrated by her conduct toward Orlando when they first meet at the wrestling challenge match ("we will make it our suit to the duke / that the wrestling might not go forward." 1.2). Also notable is her friendship and love for Celia (though some may assert Celia's friendship and love for Rosalind has more devotion) and her initial fear at being cast by King Ferdinand from his court and her home (the only home she'd ever known since her father was the deposed King): "Alas, what danger will it be to us, / Maids as we are, to travel forth so far!" (1.3).
Some of Rosalind's characteristics that transcend gender are the qualities she begins to show after Celia has shown the way and led them in taking disguises ("'ll put myself in poor and mean attire / ... / The like do you" 1.3) and making the arduous trek to "the forest of Arden." Through the trek to Arden, while wearing the liberating attire of a young lad with a "gallant curtle-axe upon my thigh, / A boar-spear in my hand" (1.3), Rosalind becomes brave, assertive, and outspoken, thus putting her woman's wit to work in addressing others' grievances. This is seen in the following. Upon entering Arden, Rosalind, though on the verge of tears herself from braving possible dangers and from weariness, comforts Celia/Aliena, saying:
I must comfort
the weaker vessel, as doublet and hose ought to show
itself courageous to petticoat: therefore courage,
When they meet Corin and Silvius, Rosalind takes the lead in asking for food and a resting place ("where we may rest ourselves and feed / Here's a young maid / ... / faints for succor." 2.4) and later on in securing a cottage: "Buy thou the cottage, pasture and the flock," (2.4). Later Rosalind is outspoken in her dealings with Orlando, for example, when they finally meet up ("I would cure you, if you would but call me Rosalind" 3.2). Another example of her outspokenness is later with Phoebe when Phoebe is so unfortunate as to declare her love for Rosalind/Ganymede; Rosalind declares: "it is my study / To seem despiteful and ungentle to you" (5.2).
I'm not familiar with the quote you use at the beginning of your question or how it relates to your assignment. However, the main character traits of Rosalind are traits that many of Shakespeare's heroines, especially the comic heroines, share. One of Rosalind's main traits is her wit. She is outspoken, forward, and clever. These are not necessarily traits one would be looking for in a good wife in Elizabethan England. They are, however, traits that Shakespeare seemed to prize in his female characters. She is certainly independent as well; she leaves the safety of the court and goes out into the forest to find her father, choosing to dress as a boy to make her way more easily. She is also imaginative and resourceful, two other traits she shares with Shakespeare's heroines. Add likable, and you have the qualifications to be a heroine in a Shakespeare comedy.