My favorite place in summertime is Bandon - lots of people go there, but it's never too crowded. The town is cute and the beaches are great. Diamond Lake is great to bike around, and if you're really fit, you can bike around Crater Lake. The road from Roseburg to Diamond Lake (North Umpqua Highway, Rt. 138) has lots of camping and hiking areas.
Honeyman State Park near Florence is great and there is a Darlingtonia preserve right near there (the plants that eat bugs). Oregon has so much to offer - if you go to www.oregonstateparks.org you can find TONS of info broken down by area. Have a great summer!
They say that time changes things, but you actually have to change them yourself.