If you cut strips down you could do a mini scrappy table runner. If you cut all the rows. Ie right angles to stripes same with as pattern says your quilt will end up same width but longer due to jelly roll size.
You could add 1/2" to each row cutting which would make it bigger in both directions.
Hope this makes sense . Recap as jelly roll stripes 1/2" wider need to make each opposite cut also 1/2" wider to keep pattern as seen .
If you just join jelly roll then cut opposite stripes size in pattern the whole pattern will be wider than pattern in one direction and same size in the other.
If you cut stripes down to 2" and follow pattern cuts in opposite direction as pattern then you will finish at the size of the pattern.