It isn't so much gender roles, wearing dresses and makeup and wigs does not a woman make. Gender identity disorder manifests itself in many ways and while a good portion of trans people choose to embrace the "typical" gender roles and appearances of the identity they feel inside they are not required to and many in fact do not. We have no "test" for being transgender, the science is simply not developed enough so we have to rely on a persons self proclaimed identity. If a person wears tshirt and jeans and doesn't wear makeup, but has a female identity and claims a female identity, then they are female. Most cisgender people don't understand the concept of gender identity because they are so comfortable with their own they never see or question it. With transgender people the issue is something we are painfully aware of 24/7 it slaps us in the face every single day. Every time someone misgenders a trans woman, or calls us a "tranny" or a "shemale" or things of that nature it causes real emotional pain. As is often said within the trans community sex is between your legs and gender is between your ears, when the two are the aligned it is hard to see a difference between them but when they are not the difference is as clear as day. I hope this helps.