Jeff,
Dr. Bob Sloan's book on a Century + 10 of D&RG Freight Cars should have the information that you are looking for. He has drawings of the 3000 series box car, plus photos of them as received by the D&RG.
They were pretty much a standard AC&F design. The only real difference between the D&RG Cars and the C&S cars of the same era (from the same manufacturer) were the brakes (C&S used New York and D&RG used Westinghouse) and the trucks (C&S used a 4' Diamond Arch Bar and the D&RG used their common standard 3'7" flat top arch bar trucks).
Yes, the roofs were wooden as purchased.
The book is currently being reprinted by Tim Mulina, who does the "quick Pic" books on various pieces of rolling stock.
Rick Steele