First of all, welcome, Tonya! Good to see you on here.
I don't know about a difference between the genders as far as rolling. As you say, it would be about weight distribution rather than shape... the male and female bodies are not so dissimilar in respect to the general shape involved in making the roll (leg connects to hip to torso to shoulder to arm to hand).
But weight distribution could make a difference, in the shape of the roll and the speed, ie, where the weight is during the course of the roll.
Personally, I have found in teaching rolls that when someone feels like they have a couple of corners on their bodies, they tend to make the roll smaller. I think this exascerbates the problem, as parts of the body meet the mat before-time. Of course, over-extension does not help either, as the person is not ready to support such a roll with their form. It has to be a natural roll, sized to the person, without any attempt to shorten or lengthen it.
I have to say, it is a pet peeve of mine to see people rushed through their ukemi/rolling learning curve, or to see them left to themselves to try to figure it out on their own by trial and error (not only for the obvious reasons, but also for reasons outside the scope of this discussion). I hope this is not your situation, but you are doing the right thing in seeking out advice like this. I just hope my opinions help.
Anyway, the roll is in you. Like a sculptor chiseling away at a square block of marble - taking corner after corner away - each roll will get better. So, as far as upper ranks who seem to roll without effort, don't think that they didn't struggle with their rolls, too. We all did, and sometimes still do! *g*