The Roach river flows for six miles, starting at a dam on First Roach Pond at Kokadjo, Maine to Moosehead Lake. Moosehead lake is the largest body of fresh water entirely contained within a single state, so I'm told. Said lakes holds Lake Trout, Brook Trout, and Landlocked Salmon, to name a few species. Of these, the brookies and salmon ascend the Roach to spawn each fall, making them accessible to the willing fly fisherman. The Roach river is fly fishing and catch and release only.
Under normal to low flow conditions, I'm told that the Roach is considered a small river, easily fishable with a 4wt rod. Along the six miles of river, there are 12 'pools' in which most of the fish congregate during a typical fall. These pools can be nymphed, fished with streamers, or with a dry fly if the situation calls for it. The rest of the river is strewn with boulders and I think typically too shallow to hold a lot of fish. I could be wrong about this because I fished the Roach last week (late Sept) under very high flows. The high flows seemed to spread fish out a bit, and made it impractical to nymph given the faster water and boulder substrate, it seemed I was either hung up on a rock or floating along the surface. It didn't matter, because under these conditions, you'd be a fool not to be swinging a streamer.
I believe the locals call this the ledges. It was the best holding water I found. It was sweet.
First light on the Roach River. Most of the river looked like this, strong current, fish holding in the softer water (not shown)
I took a rental car from Bangor up to Greenville and stopped in at Main Guide Fly Shop. There I got some helpful tips, a couple of flies and directions to free a campsite near the mouth of the river.
One of the flies I picked up is called the Shufelt Special. It is just a simple attractor streamer: orange body with a white wing. It might resemble a brook trout fin, not sure, but it rocked.
The Shufelt Special, wet. In a day and a half of fishing I landed a dozen brook trout and one landlocked salmon, all on streamers and nearly all on Shufelt Specials. I lost a couple of fish on small soft hackles (suggested by the fly shop). The salmon didn't want its picture taken and flopped away before I could snap a pic. It was a good 16-18 inch fish.
Most of the fish I caught looked like this:13-14 inches and fat. 
This was the fish of the trip, a big bright male brookie that took a streamer swung right in it front of its face. I am a bit disappointed that it didn't take a better photo. But that's how she goes. I landed a couple of nice males in bright fall colors.
The Roach River is awesome. It is pretty remote and very hard to get around on, making it easy to find your own piece of water despite the fact that it is only 6 miles long with 12 pools. I'm not sure if I'll ever get back there, but if I do, I'll spend a lot less time searching for water and much more time fishing.
