If your six border stitches (first 6 and last 6) are garter or seed stitch, it should not roll.
Garter stitch is simply knitting each row. For example:
Row 1: k6, row 2: k6.
Seed stitch is done like this:
Row 1: k1, p1, k1, p1, k1, p1.
Row 2: p1, k1, p1, k1, p1, k1.
If you didn't start with a purl on row 2, you'd get a rib effect.
Hope this didn't confuse things.
