Just sit down and roll / rip up / roll over and over again until you get it. Form the joint with the paper before you start actually rolling it up. Work one side, then the other, then the center. Rolling a coned shape is easier than a straight joint. The best tip I've learned is lick the outside of the paper after it's rolled to avoid licking off the gum. It also lays the edge down flat and straight.
Joint rolling machines make me feel like John Henry. I'm the greatest roller east of the Rockies.