I've had this rolled hem foot (aka hemmer foot) for a while now. Unfortunately, I have yet to master the art of the rolled hem. Try as I might, I can never seem to produce consistant hems with this foot. I end up with fabric peeking through, or either I don't roll enough fabric through and the hem comes loose.
I really want to be able to use this foot. It is MUCH faster than doing a narrow hem (so I'm told.) I'm ashamed to admit it, but I've spent a total of 90 minutes fidgeting with the fabric and the foot trying to figure out where I'm going wrong... and I still can't produce a consistant hem.
See what I mean? Sometimes it's beautiful, and sometimes it's not. I found a great tutorial here that explains how to use this foot. I hope you have better luck with it!