If I recall correctly, the coffee provided in the rooms is the kind that is already in a packet. The basket, I believe can take the small flat-bottomed filters (not the cone shaped). I have to admit, though, we rarely use the in-room coffee maker. We would rather walk to the GCH (short walk from Fiji) and get coffee there (or send our children, since our kids are now at the age where they can go by themselves, so they always bring Mom and dad back some coffee).
Enjoy your stay. Aloha!