Social roles do not develop in a vacuum. They are, in large part, based on biological differences.
Well, yeah. Humans are animals, and pretty much all species have traits associated with each gender, so it would be a bit silly to assume that we're magically exempt from this. Thing is, there's a difference between saying, "On average, members of each gender will possess the physiological and mental traits needed to fill specific roles when facing survival situations" vs "Boys who like the colour pink are pussies."
Likewise, it's important to recognize that many roles were originally based around necessity back when survival was actually a major struggle for our species. Without those restrictions in place, people are much freer to explore aspects of their physical and psychological makeup that don't align strictly with what's
average for their gender -- something I'd consider a positive, being that it gives all of us the opportunity to live lives that are much more fulfilling, and give a larger number of people the chance to contribute to human progress in a variety of different areas.