I built myself a filament dryer by creating this separator for use with a 5-star Chef Food Dehydrator. One separator is placed between each tray of the Chef to make sufficient space to insert a roll of filament on each level. Print 5 of these separators and you can dry 5 rolls of filament in a single go. The scad file is parametric, so you can modify if you want to play with the dimensions, and it should auto-configure as you change bits and bobs. I spent some time making sure the default arrangement has all the bits exactly the right thickness so that all parts fit together (including the inside tabs) snugly. You shouldn't have to change it. One of the pictures shows the profile of the part, so you can see how it's not just a straight-edged cylinder.
Here's a dodgy assembly video....
Edit: Note that these SHOULD work as stackable cylinders for use in other applications. Just change the dimensions via the parameter variables and I reckon you'll be good to go.