Both of these hems work well on the more delicate, sheer fabric like chiffon and lace. The rolled hem, I believe, is the more common one and you can probably get a rolled hem foot from your sewing machine dealer pretty easily. The difference is the rolled them is turned (or rolled) over twice. The picot hem is only turned over once. From the old school, original way to get a picot hem is to first to do a hemstitch along the edge to be hemmed. Then cut the hemstitch in half, turn the smallest measurement of fabric to the wrong side and sew into place, usually by hand. If there’s a foot for picot hem, I’ve never seen it. I think these days with the advancements of sergers and sewing machines that can finish a raw edge, it’s not really done as much.