Can I Tyvek before dry-in?

I'm building an addition myself except for the roof framing. However, the carpenter I had a contract with, and contrary to the agreement, can't come for another two months! Finding a replacement on short notice is next to impossible. Moreover, the framing and plywood sheathing on the walls were soaked during and after Isabel and it finally dried out so I really want to get the Tyvek on and prevent the wood from getting wet again. The question is: Can I install the Tyvek before the roof framing and roof? I can stretch a tarp on top of the second floor joists to keep precipitation out and I can also install the windows to close-off the sides. Any thoughts would be greatly appreciated!!