Here is a link to a group known as "Come Ride With Us".
They are located in John Day Oregon and they have produced some real nice FREE maps for Eastern Oregon, Central Idaho including some SE Washington, NE Oregon and SW Montana, and Southeast Washington and Nofth Central Idaho including some NE Oregon and SW Montana.
I picked up one of there maps at a grocery store when I was in Heppner. I have plans on going back and exploring more of these fine roads. On the map Red roads are "paved", Blue roads are "gravel".
I hope some of you find this resource useful. Note you can zoom in on the maps about 4 times and then they are easy to read.
Click HERE to See Maps