Gina, Highway 199 (CCto GP) is usually clear, but should you decide to continue up the coast, 101 is easy, with lots of stopping spots. From experience, the best road across from the coast to I-5 is from Reedsport through Drain. It has the most passing lanes which make RV towing much less worrysome. It puts you back to I-5 about 35mi south of Eugene. This of course by-passes the Rogue Valley but also cuts out the 4 passes between GP and Roseburg. If the weather and highways aren't bad, going all the way, to travel the coast route will add 10-14 hours to trip time so keep your options open. They do try to keep I-5 open day and night but often require traction devices on each of the passes, which if using chain type, can be a a hassle on and off.
Wish it was July for your travel!!!! Renee