Everything I've ever read about writing a rough draft goes something like this: It's just part of the writing process that you must write a load of garbage first. Get a crappy version of your idea on paper. This is your rough draft. Once you have it, you can revise.
I've tried this approach. And it doesn't work for me!
One reason is I edit and revise as I go. "They" say don't do this, but honestly I can't stop myself. It's just how I work. Another reason is I can't bear to waste time knowingly writing crap. I strive to write something better than crap at all times!
That's not to say I always succeed. ;)
My personal approach to the rough draft is a little different. Last year, I wrote an enormous brain dump of ideas based on a character and a loose story idea. It didn't remain cohesive for long. But I kept going in order to get every thought and theme out. It took a few months. In the end, it was a rough draft of... nothing. At least that's how it appeared at first. I never went back to revise that particular pile of pages. There really wasn't anything there to revise. It was what every writer is supposed to aspire to in a rough draft: junk!
BUT this became sort of an all-encompassing rough draft for several future projects. It freed me up to write a middle grade novel. It sparked ideas for two YA novels.
The lesson: Don't get caught up in other people's advice about how your writing process should work. It's all just guidance.