shone73,
You've received some good info on the source of your rifle.
I respectively offer a few other comments and things to look for.
The "G. Roberts" engraved on the barrel could be the Greg Roberts that worked for Green River Rifle Works of Roosevlet, Utah. In the day, Roberts often marked his guns with an engraving of a bear paw as his makers mark like this one.
The absence of the makers mark does not rule out the GRRW Greg Roberts as the builder, but makes it less likely.
Another thing to check on the rifle is the number of lands and grooves. GRRW rifled their barrels with 7 lands/grooves. If your rifle has 7, it would strongly suggest it is a GRRW barrel and Greg Roberts was the builder. If it doesn't have 7 lands/grooves, then it likely wasn't made in the 1970's by a GRRW hand. Though, this doesn't rule out Greg Roberts building it at a later time.
The lock, and especially the hammer, looks like a Hawken lock of fairly recent manufacture from L&R. The L&R Hawken locks back in the late 1970's had a different hammer. This suggests to me that your rifle post-dates GRRW.
Naphtali mentioned Greg Roberts of The Hawken Shop in Oak Harbor, Washington, might be the signer. I agree that might be a possibility. Though not listed as a catalog item, I've seen one other full stock Hawken that was reportedly made by The Hawken Shop. You could send pictures of your rifle to him and ask him.
Your rifle appears to have a short barrel and only has one forward ramrod pipe. This suggests it has been shortened or was built to appear that it had been shortened.
Others pointed out the unusual single trigger set up. This is not what we typically expect on a Hawken rifle, but I know of a couple original Hawken rifles that have single triggers. Could have been someone's whim or could have been an effort to emulate one of these known originals.
The fit of the hooked breech to the tang is not as good as I've seen by GRRW riflesmiths. Another reason I would question whether it was that Greg Roberts.
On your request for some info on GRRW, they started operation in March of 1972 and were forced into bankruptcy in the fall of 1980. Greg Roberts was the General Manager during most of that time. GRRW are best known for the affordable half stock Leman rifles they called the Leman Trade Rifle, their half stock Hawken rifles, and their high quality barrel business. They made other models such as full stock Lemans and Hawkens, a Poor Boy (Southern Mtn rifle), and a Trappers Pistol.
The rifles that GRRW built in their first few years of operation were stamped with "GREEN RIVER RIFLE WORKS" over "ROOSEVELT, UTAH" on the top flat. The guns normally had the caliber and serial number stamped on the left oblique flat near the breech plug. The Leman Trade Rifle serial number started with 101, while the half stock Hawken serial number started with H-001. After a few years, the company stamp was changed to "GRRW" over the address. The "H" prefix was dropped from the Hawken serial number, and the individual riflesmiths started marking the barrels with their makers mark.
All factory finished GRRW guns had the company stamp and serial number somewhere on the barrel, usually on the visible flats, but sometimes on the bottom flats if requested by the customer. GRRW sold semi-finished or in-the-white rifles that also were serial numbered and usually had the company stamp and address. Lastly, they sold "basic" kits which were normally a parts set. These were not serial numbered and most often had no markings on the barrel other than the caliber stamp.
Some of the smiths built rifles on their own time to sell for their personal income. We see some of these rifles from time to time. They typically are made with GRRW parts and have the builders makers mark, but no company stamps or serial numbers. Some smiths continued to make GRRW like rifles after they left the company with parts they had accumulated while working there. The rifle that necchi linked to at
River Junction is an example of one of these. A few smiths eventually formed businesses of their own and made rifles very similar to what GRRW had made such as Oregon Trail Riflesmiths.
Phil Meek
GRRW Collectors Association