Here's a good place to start.
http://www.modabakeshop.com/search/label/Jelly Roll
I'll see if I can find a picture of my French Braid quilt. One jelly roll will usually make a small quilt. It all depends on the pattern. If you use a lot of background fabric then you don't need as much. I suggest you choose your pattern first before purchasing your jelly roll(s). Sometimes I find I want to make a quilt and it needs a mix of jelly roll and layer cakes and all I bought are jelly rolls or vice versa.