it's not necessary to wash except for flannels, which ALWAYS shrink...but I do strongly encourge you to use an all or nothing philosophy to keep yourself happy - if you wash one of the fabrics in a quilt, wash all of them. If you don't want to wash fabrics, make sure none of them are washed. In your case, since you want to use a jelly roll as part of the quilt consider whether the other fabric is washed or not. If other fabric is washed, you should wash the jelly roll, but you can do it gently so you don't lose that edge to fraying...soak it thoroughtly in hot water, for example, or wash it on delicate cycle inside a laundry bag or pillowcase, etc.