You never said where you are going, so I can only assume that it is the state park. You might consider Salem to Cloverdale and pick up 220. Turn off of 220 onto 221 to Bedford, then 122 to Moneta. You're on your own from there. There is no way I know of to avoid the mountains but at least it gets you around Roanoke, and possibly on the side of the lake you need to be on. (However, 122 does cross the lake.) Hard to say if this would be a better route for you, or not.
Happy Camping! ///// Richard D.
2006 4x4 Ford 250 SD / 2007 Flagstaff 827 FLS
One very patient wife and one furry child who travels with us. Forty-two years of trailering and camping, and I still have a blast.