This guy has a lot of ride suggestions for Oregon.
Home Page - Jay's Essential Bike Rides
There aren't a lot near Crater Lake though. Many years ago we spent a few days in Ashland and I did both of the rides on this site near there. Local clubs refer to one as the lakes loop and it is really nice IMO, I've also ridden the old highway and on up to Mt. Ashland ski area and that is a good ride too.
Heading north only one I've done is from Sister over McKenzie Pass to the the intersection of Highway 126 and back, really a stunning ride. We got lucky and got to ride it without cars before the road opened in June last year.
Another ride mentioned on the site is the Aufderheide Highway near Eugene that is supposed to be really nice.
I know there is someone that posts a bit on this site about rides on forest service roads in Oregon, there seem to be a lot of them that are paved and have very low traffic. Might try searching for those.