For what it is worth, 30' D&RGW narrow gauge freight cars (boxcars, stockcars, gondolas) right around 11 tons empty. (ie 300 series boxes, 5500 series stock cars, and all of the highside and drop bottom gons)
The earlier cars (such as 24' and 27' boxes) weighed between 7 and 9 tons, while flatcars weigh quite a bit less (even the 34' long D&RGW 6200 series flats only weighed 8 1/2 tons as built and something like a West Side 24' flat probably weighs 5-6 tons)
Not sure what the Roaring Camp passenger cars were built from, but it would seem that 10 tons would be a reasonable guess as to their empty weight.
Jason Midyette