i usually do not prewash my cotton fabrics but i will prewash some of my batiks. the dye process in some batiks allow the colors to run and i would not want that to happen after i make a quilt.
i have found that CT fabrics do unravel a lot more than other fabrics i purchase. for precuts (rolls or charms) that i purchase from CT, i handwash those. i swish them around in hot water, rinse and squeeze the water out.
good luck with your projects.