It seems appropriate to use one of Bonnie's quilts for this so here is Razzle Dazzle all laid out and ready to roll.
Bring one corner over, leaving enough at the ends to give you HALF of your desired finished length of roll. Notice how it not brought even.
Now bring the other side over, again keeping HALF the desired finish width. At this point you will see your finished width and can make adjustments.
Fold the center section back on itself.
Starting at one end, tightly roll. (Yes, my foot is keeping it in place for the picture.)
Continue rolling, keeping smooth as you go.
Here is you finished product. I have personally watched Bonnie do this to the size of whatever packing box she wishes to use and believe me, the box is much smaller than you think a quilt will go in.
A quick moment later and it's back in the cabinet, waiting for the next time I call upon it's use.