Roller mills are the ultimate in achieving precise particle size distribution. I have a dozen or so years experience with them in the printing ink industry, but they are also used for grinding cacao into chocolate, grinding various flours and many other industries where you need to turn big particles into small ones.
are the mills I mostly worked with. The important thing with roller mills is that if you want to get precise particle sizes, the gap between the rollers has to be exact. Grinding relies on friction, friction produces heat, so all the rollers have internal cooling systems (usually refrigerated water) built in. When you're dealing with micron sized particles you DON'T want the metal rollers to expand or contract with temperature changes.
There are "laboratory" versions of roller mills produced by the same companies that make the production mills. They generally come with reverse cycle heat exchanger systems that need to be plumbed and wired in, and $10k+++ price tags. This is definitely not an industry suitable for amateur involvement, just producing the rollers requires a megabuck investment in technology.