I've been ordering and visiting some of these roasters at their businesses. They're small, and very knowledgeable. They're worth a visit or an order to test them out.
Koffiestation - Groningen
Small roasters that deliver by bike in the city of Groningen. They have a great starter pack and tasting pack.
Black and Bloom - Groningen
Winner of several awards with a very cozy shop near the university. Also sells great baked sides.
Fascino Coffee - Weert
Medium sized roaster with a great consistent set of beans that you can rely on.
Kahawa Pakaya - Norg
Speciality coffee from the eastern countries in Africa. Great flavours in pretty packaging.
Moyee - Amsterdam
Hip and vibrant packaging, they sell a coffee subscription that uses a different microlot every time. Their regular coffee is very reliable and well balanced.
Rum Baba - Amsterdam
Bold and unique coffee flavours. Delivers by bike in Amsterdam.
In Amsterdam: I get my daily espresso coffee beans from Five Ways, and whenever I feel like taking it up a notch I try a bag from Uncommon. Highly recommend both.