From what I understand a roller on the mower pushes grass in one direction then when you come back the other way it pushes the grass in the other direction but you need a rotary mower for this.
Another way to do it (yes guys I have too much time on my hands some days) is to cut at a different lengths just watch out it becomes addictive then other people will start doing in the street then you stop and everyone else does quite funny really.
You could also make up a roller and attach it to your mower as well PVC pipe filled with sand would do the job.
Some mulcher mowers can do it as well if set up correctly I have been told.
You need to get the lines right though as it just looks stupid if you dont :cheers
Yes you can say :dougy: I understand :fergo: