(I don't mean to have everything here underlined but I can't seem to fix this problem, so I'm sorry, but I have to post what I have to post. It is obvious I have a lot to learn, so please bear with me). When crocheting scarf using stockinette or garter stich, the edge rolls. So to fix this problem, I turn the crocheted fabric (ws) wrong side up and crochet 1 to 2 rows/rounds of the edging, then crochet (rs)right side up next and (ws) up alternately. This makes the edge to lay flat and not roll towards the right side of the fabric.
The photo shows a portion of a crocheted scarf (wip) with the (wip) edging. A photo of a knitted scarf with crocheted edging is shown in "tips and tricks" section of Crochet Me.