For large fixed-blades you're limited to a zipper pouch; I doun't know of any roll-up products for fixed-blade knives. For folders, the Sack-Ups are a good choice.
Personally, I keep all of my knives in the original boxes, if available. If the knife didn't come with a box or pouch, then it's into a Sack-Up, zipper pouch, rolled in Kleenex, or knife roll case.
If you have a significant amount invested, you should consider a gun safe or some sort of locking cabinet. The worst ass-pain you can imagine is trying to find exact duplicates to replace even a small knife collection. It took me 13 years to locate duplicates for a dozen knives that were stolen once.
Best Wishes,
-Bob