The DPN roll will also fit 8" needles. I goofed when I made one for Stringcat -- I misread her post and made one for 6" needles instead of 8" needles. But the longer ones fit okay, too. I really do want it to be a bit longer, so the flap folds over better, but there was at least 3" of flap, so it should work fine.
I made a roll for Ibby, too. She didn't want as many slots in her roll, so I cut the fabric at 15" instead of 19". This gave me 12 slots for DPNs.