Here’s the thread from a couple years ago showing the roll I made for my Leatherworking punches. Basically, you fold in the sides of the roll to make two layers, then sew pockets out of those layers. Pockets for knives would obviously be larger.
For a knife roll you might only put pockets on one side and leave a loose flap to cover the handles on the other, or alternate the pockets on both sides so the knife handles interleaved.