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.
Black and Bloom is my favorite, especially in the afternoon after doing some shopping in the Grotemarkt. The owner is very friendly, he talks about coffee beans with a passion. Highly recommended.