One thing I've done and liked, is to pick up stitches along the bottom edge, and knit an inside hem: Knit a row plain, then on the next round decrease 10% of the stitches, to prevent it from being a bulky hem. Knit for an inch or inch and a half, then just whip stitch each stitch to a purl nub of the inside of the garment. Don't do this tightly, or it will gather or show.
So, in case this isn't clear: this hem is worked in stockinette, and is folded up inside the garment and bound off by sewing to the garment. This is how I hemmed the Bumble Bees Sweater shown here. As you can see, the hem shows as a thicker bottom, but looks good, no problem with rolling.