It is my feeling that piano roll cabinets should have a shelf for each
layer of rolls.  Rolls piled on top of each other is rough on the boxes
and many are damaged while trying to pull a roll out from under others
on top of it.

Original roll cabinets were designed so the shelves are about a quarter
inch shorter than the roll boxes.  This allows one to grasp the roll
easily and remove it without danger of damage.

As my collection outgrew the original Ampico Roll cabinet, I found 1920's
china cabinets to be just right for roll storage. In many instances the old
wooden china cabinets can be found inexpensively at thrift shops or garage
sales. Some are the correct depth for roll storage. If one is handy with
tools, the interior sides can be dadoed using a router and individual
shelves fit into place. Shelves should be at least 3/4" thick to prevent
sagging if the width exceeds three feet.  The shelves should be spaced
high enough to accommodate large roll boxes with a half inch to spare.

Bruce Clark