First of all, I know nothing of this area, but if I was looking at a map and I was leaving Roseburg for Gold Beach, I might take that road through Riddle, Glendale, to Galice,Agness, then to 101 and to Gold Beach. The link doesn't say what # road that is.
Oregon Highway 42 is an Oregon state highway which runs between U.S. Route 101 on the Oregon Coast, near Coos Bay, and Green, a few miles south of Roseburg on Interstate 5. It is known as the Coos Bay-Roseburg Highway. At Coquille, there is a split in the route, as Oregon Highway 42S heads southwest toward Bandon. The largest towns on the route are Winston, Coquille, Myrtle Point, and Green (which is actually unincorporated). Highway 42 serves as the southernmost link between the Oregon Coast and the Interstate 5 corridor.http://www.answers.com/topic/oregon-state-route-42
I was looking at a Mapquest map just now and my instincts, not knowing, would have been to leave I-5 at that Merlin cutoff and take Merlin Rd west or Monument Dr. south (whichever one comes out of the freeway) to Galice Rd. and then west to Galice and Agness.
Those are marked "Nf-23 and Nf-33, as well as Blm38-4-36" or something like that (from memory on the BLM one). That must mean those are National Forest roads and a BLM road.
Then, towards the coast, it's marked 595. It follows the Rogue River all along. Looks treacherous to me, just the way it meanders on the map!
However, it *is* the straightest shot from I-5 at Roseburg to Gold Beach.
Bless their hearts.