Fusible thread aids in making a narrow rolled hem.
With this thread in the bobbin, stitch (long stitches OK) on RS of fabric 1/2 in or so from edge of fabric. Fusible thread should be visible on WS of fabric. (See photo above.) Press hem up using stitching line as a guide with crease just above stitching line. Trim 1/8" or so from crease and turn up again. Put regular thread in bobbin and make the final stitching line. The fusible thread helps hold the crease. Often I don't even have to press the hem up for the final stitch but do it but finger press right at the machine as I stitch.