the Blacks creek area is a mix of BLM, private, and state land. its interesting to look at a map cause you can see spots of private land that was bought by someone years ago but no access into it and completely surrounded by state and BLM
There are some good trails up round Rocky Canyon. Some are skinny, but there are some that open up and you can go full boar on them.
One of the roads to Rocky Canyon is off Warm Springs on Reserve Street over by Fort Boise, the other way in is to go up through Council Springs which is dirt all the way. It's BLM land so it's closed for part of the year, there are trails that sprout away from the main road so you can get as lost as you like up there.
Robie Creek is not very good right now, try it in the fall, couple of weeks after they've drained it. The mud is pretty thick and there is lots of it.
Just some ideas for your offroading pleasure.