Rollers should have some speed to them, though I do not know whether this is too much or not. I am sure however that this is the right direction: Against the movement direction, forcing the powder up. This is how all powder printers do it. If you roll with the powder, it might jam or over-compact.
I would like to have used a small DC motor, but there simply isn’t any room. This system seems to work just fine for now and it has the added benefit of having no additional motors.