So far the only jelly rolls I have purchased have been batiks. They have been the smaller ones with 24 strips that Walmart has. The batiks have been the only ones that I felt were ones I could use.
So I guess my 'perfect' jelly roll would also be batiks. I would prefer all the fabrics in the roll to actually work well together. It seems like there's always one that just doesn't quite fit with the rest and gets set aside. IF there are duplicates, then an equal number of each...not 4 of this one and 3 of that one and 2 of something else. But I agree that all different but coordinating would be good.
I also like the suggestion of a group of blenders in various colorways. Although I think the blenders might be better in larger pieces than a jelly roll. . .maybe 1/2 yard pieces of the coordinating colors.