Gender roles are a form of conformity. When we abide by or emulate them, we allow others to define the way we choose to express our being inside and out.
From the moment we are conceived, roles and expectations are drilled into our brains. Anything associated with being male automatically assumes a dominant position. Girls, on the other hand, are taught to assume a more submissive identity. These assignments are used to assert who has the ultimate power arrangement. Many queer relationships, by virtue of their same-sex makeup, undergo a struggle for who should assume this power.