Fuji Roubaix Pro sold for about $1,500 should have Ultegra, aluminum frame with carbon seat stays, and is four years old. I would say offer the guy $400, and maybe he will give in. You have to make sure the bike has no dents and that the shifters and brakes work well.
http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2006&Brand=Fuji&Model=Roubaix+Pro&Type=bike
http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?Year=2006&Brand=Fuji&Model=Roubaix+Pro&Type=bike