Even with a roller, directions could matter. I understand the 'self-filling' properties of the material, but using a different direction each time will give a stronger result.
Think of fiber-glassing. if you'd apply all the fiber matting strips in the same direction or you'd put them alternate horizontal and vertical. Same for applying paint or permadri coat, the layers will fill better by alternating direction.
It's just a matter of eliminating all possible reasons for a leak to occur, so I'd try it unless the manufacturer tells me not too.