Using the EB method, which is 3 rounds and makes a 14" finished block, and assuming you use every inch of 40 strips (not realistic I know) you could make 15 blocks with a Jelly Roll. If you figure in some waste on each strip, you should still be able to get 13 or 14 blocks out of your roll. Twelve blocks would make a decent sized lap quilt if you add some borders.