You can wash jelly rolls, but test the method I am suggesting on scraps to see if you like the results.

Safety pin 5 jellyroll strips together, End. Middle, other end. Do this until all strips are pinned. Put them in a lingerie bag, zip it shut. Wash in cold or warm water on gentle. (Use color catchers if you want.)

When done, hang individual strips over towel racks/shower curtain until dry.

I rarely do this, though.

Bearisgray, I've wondered the same question you posted many times! but my answer has turned out to be pretty much like LI diva's. I prewash as much as practical for any fabric that will go into a quilt I expect the user to be washing, hoping it will shrink/bleed less for the end user. I'm a new quilter and only made 5 quilts so far. I haven't washed jelly rolls because it seems like they'd just end up a frayed mess. I figured, if a good portion of my quilts would already be preshrunk, it wouldn't be the end of the world if some jelly roll bits shrunk a little after the quilt was finished. It turns out that in the quilts that have both jelly roll (not prewashed) and yardage (prewashed) intermixed -- after washing the finished product, it's just fine! The quilt is still straight, the jelly roll parts aren't apparently shrunk out of proportion to the prewashed parts. So, I'll keep on prewashing stuff FQ or bigger, but not worry about prewashing tiny precuts.

The only reason I wash pre-cuts is because of the chemicals effect my fingers. So I use a small amount of Woolite or Dawn dish soap in my large salad spinner. Make sure it is well rinsed, spin, hang dry. I haven't worried about shrinkage, just the chemicals. If it's a small project that I won't be working for days on it - such as a Christmas stocking size or a small table runner, I don't pre-wash, I just wash my hands after sewing.

I just avoid buying those strips and small precuts.

It is important to me to try to avoid unpleasant surprises like bleeding and shrinking.

I have had enough of those in the past.

What is surprising to me is how few other people have seemed to have these issues.