If the sweater still rolls after blocking, you can pick up stitches along the bottom, and knit a hem. Just pick up one stitch in each stitch with the work facing you, knit or purl a row (for stockinette stitch facing out), and then decrease 1 stitch out of ten in the following row (work 8 stitches, k2tog, repeat). Then knit plain stockinette for an inch or so, and sew it stitch for stitch to the purl loops on the inside of the sweater. The baby bees sweater I have on the patterns page was edged this way along the bottom. It's also a fun opportunity to knit a hidden design, like the child's name, into the hem, like Elizabeth Zimmerman used to do. Just chart out the letters on graph paper. Fun!
KnittingHelp Queen Bee
"There is a vitality, a life force, an energy, a quickening that is translated through you into action, and because there is only one of you in all of time, this expression is unique. And if you block it, it will never exist through any other medium and it will be lost. The world will not have it. It is not your business to determine how good it is nor how valuable nor how it compares with other expressions. It is your business to keep it yours clearly and directly, to keep the channel open. You do not even have to believe in yourself or your work. You have to keep yourself open and aware to the urges that motivate you. Keep the channel open."
— Martha Graham