Well... I don't know what to tell you, honestly. I have basses with necks like the ones you've mentioned - including a roasted Maple/Rosewood one on my '20 EBMM 4HH Stingray Spl. (I quite like that one); laminated Maple/ Something that slips my mind/Maple ones - with different somethings; and Aluminum ones with Ebanol fretboards. Frankly? I don't really pay much attention to what my bass' necks (or my guitar's necks, either) are made of. As long as they're strong enough to do their job; the fretboards hold the frets securely; and the whole thing don't give me splinters? I'm a happy camper. However... I guess I'd have to say that it would depend on the bass' finish. IMO, Ebony - black Ebony - doesn't go well with a really dark bass; although it can look quite striking on a light one. My Lexus Pearl White Carvin LB-20 is a knockout with the MOP block inlays in the Ebony fretboard. Looks good on my Orange Gretsch Broadkaster and my Maple topped Alembic, too. Any fretboard that's a little lighter - like Rosewood, the lighter, streakier Ebony; Rick's Bubinga; or Pau Ferro - goes fine with just about anything. The Rosewood fretboards I have look... nice... on every bass I own that has one. Maple fretboards? IMO, they look too "Blah" when paired with any bass body that's too light; natural or painted. Which is why they look so good, contrasted with a 3TB finish...

So, I suppose it all depends on the look you want. Personally? If I ever build another Warmoth bass, I'm seriously considering a Purpleheart fretboard - with turquoise dot markers and bronze frets. Can't decide on the body color, though...