Is it reasonable to consider that rock music is gendered male?

Yes and no. I believe that there are two aspects to this statement. If you take rock music literally and look at the male to female ratio of rock musicians and songwriters - then the genre is clearly dominated by men.

However, if you look at the content and connotations of rock music, females have a very obvious influence; whether that be the androgynous blurring of gender lines by Bowie or the content of a typical Prince song - women were/are referenced to in rock music all the time (albeit sometimes in a misogynistic way).

Stereotypically, rock and roll is angry, aggressive, expressive – all masculine traits - and whilst it can be argued that women that do make it in the genre, such as Joni Mitchell and Janis Joplin, display very masculine traits, as Ani Difranco said “Men make angry music and it's called rock-and-roll; women include anger in their music and suddenly they're angry and militant.”