I found a map online and I guess it was I-84 that I saw the guy riding on. The map says you can ride on the CRH (Columbia River Highway) (though I would not want to ride it personally). Can I still get to Rooster Rock from the CRH? Is there a divider between the east and west roads? I assume the answer is yes but, if I had an emergence while I'm on a highway where I'm unable to cross over to the opposing lane would it be illegal to walk or ride my bike against traffic? Does any else second not riding on I-84 and or not riding on the CHR at night? It appears that the CRH eventually turns into I-84 at about Ainsworth State Park.
Here's the link to that map if anyone is interested: (PDF)
http://www.skamania.com/pdf/biking-guide.pdf