It is possible to cut 56 5" squares from one yard of fabric, so there are your first four fat quarters. (3 FQ's will only yield 40 5" squares, so not enough).
There are 1512 square inches per yard. The yardage of a jelly roll is 40" x 2.5" x number of strips (I am unaware of how many strips are in a roll). This number will then need to be divided by 1512 for yardage, then multiplied by four for FQs.