I don't pre-wash.
It's pretty easy to test for colorfastness. Drop a small piece of the fabric into a glass of water and let it sit for awhile to see if dye bleeds out. After that, rub the damp fabric against a white fabric to see if any dye transfers. If a fabric passes both of these tests, I use it unwashed in a quilt.
The one precaution I take is with the first wash of a quilt. I use Synthrapol and a washing machine that uses *lots* of water. (A home top-loader is fine. If you have a front-loader, take the quilt to a laundromat and use one of their large front-loaders.) Synthrapol suspends unset dye particles in the water so they can be rinsed away instead of settling into other fabrics. For Synthrapol to work, you need hot water and lots of it.
If a fabric fails the tests above, then it's a good idea to wash the fabric in Retayne. Retayne permanently sets dye. The bleeder fabrics that just don't stop bleeding have probably not been properly set in the factory. A few fabrics require two Retayne treatments before becoming colorfast. Any fabric that still bleeds after two Retayne treatments should not be used in a quilt.
For a jelly roll, I would simply not prewash and then be sure to do the first wash with Synthrapol and lots of water. However, some people prewash their jelly rolls simply by soaking in hot water and then laying out flat to dry.