a jelly roll is normally 40 - 2 1/2" strips of fabric- so- sewn together- just as strips you would have 40"x80" if you sewed them both together the same way then sewed those together- you could have (about) 78"x 80" (figuring some trimming & seam allowance)
if you then added borders you could make it a queen-
if you do something with the strips besides just straight sewing them- it will make it less- since you loose 1/2" with every seam
there are TONS of patterns for jelly roll quilts- strip quilts