What is the value of a rohr rg10 22cal pistol?

Honestly, and with no intent to insult you, the gun is pretty much worthless. The quality of the material and the workmanship makes most gun shops and shooters value that gun as junk and unsafe to shoot. If you are being offered the gun, pass it by. If you already own it, consider taking a hammer to it and destroying it for the safety of future shooters.