Thanks for the link. I had no idea this was still there. I found a reference to it in Gerald Best's Railroads of Hawaii saying that the Kahului Railroad built an 11-stall roundhouse between 1923 and 1926. It doesn't have any photos or say that it's still standing, but the aerial photo does show this to have 11 stalls.
Google Maps shows this to be the location of Elcco Inc, an electrical contractor. From the
street view, taken in September 2011, you can see the ELCCO sign over a back door, so they probably occupy at least a portion of the structure. An
earlier street view (from 2009) doesn't show this sign.
Steamlocomotives.com shows the current use to be Kahului Trucking and Storage, and
their web site also shows this address.
Once travel restrictions ease up a bit, I'll need to take the short hop over to Kahului to see this. It's less than 80 miles from me, but with the Maui Channel in between, I can't drive there. Fortunately there are direct puddle-jumper flights from the Waimea-Kohala airport (~ 2 miles from me) to the Kahului airport (~ 2 miles from the roundhouse).