Jw's suggestion completely explains how to untwist them. You got really lucky there. The oaks would be my first projects, save the Osage for after you have tillered some "lesser" quality wood. Decade seasoned oak fits the bill for great oak for bow making. his suggestion of using the worst piece of Osage you have as your ring chasing teacher is a good one. Even if its twisted 360 degrees with 50 knots it can serve to teach you ring chasing, how to deal with knots, following grain for laying out the bow, and seeing how much twist can be removed from an Osage stave. Carry on the bow making process as far as you can with it, even if it doesn't make it to being a bow the lessons it will teach you will be worth it.
You may want to talk to him and see if you can get one of his gnarlier staves as the few you got look pretty clean, not with messing up with practice. You won't need to chase a ring on the oak, the back is right under the bark.