Doesn't look like you got many options for paved roads between Eugene and Crater Lake. We drove up to Crater Lake a couple years ago from California, and the roads to the south were great. From Grants Pass, I-5, we took OR 234 and 62, and they were very scenic roads with little traffic. On the return trip, we took OR 62 and US 97, with similar impressions. The whole time I was driving through Oregon I was wishing that I was on a bike.