Instead of rolling the quilt, consider folding it accordian style. Or even just scrunch it up. Also, it's key to have adequate support around it -- I use the dining room table, with a card table or the ironing board set up to the left of the machine to hold the weight of the quilt.
In my experience, stitch in the ditch is actually one of the harder approaches. It's far easier to to an all over stipple in free motion, or to do a grid or "organic line" quilting. If it's an option with the style and pattern of your quilt, maybe you could transition to that and ditch the SITD.
RST