I've designed a new wall mounted filament spool holder inspired by other designs on this site. If you want absolutely no friction, you will need two M8 screws (a few CM long), two M8 nuts and two skate board ball bearings (8x22x7 mm). Some filament spools however easily unroll themself without any friction, in these cases I recommend just putting in the roller without the screws and bearings.

I've modeled this in Blender and you are free to remix it of course.

You can find a Blog post about it on https://m8geil.de/posts/3d-print-filament-spool-holder/

For dovetail mounts for the M4 nut holes on the sides see also this file: https://www.prusaprinters.org/prints/131594-makergrid-dovetail-mounts