If you look at the thread on 'Under cover farmers' and watch the video, you will see that they are into cover crop blends with a high number in front of them -- 9-way, 12-way, 17-way -- just a little bit of everything. I'd add chicory and clover and radish and vetch and maybe some winter peas to your turnips to round out the mix.
It really depends on how cold your winter is going to be (like that is going to be easy to predict--NOT!). If you have a mild winter like 2012 was, then little of that blend will winter kill and you will have to roll it before you plant next spring. If it is a typical cold Kansas winter with a lot of snow, it should all be dead by the time spring comes around and you will have a good mat of decaying mulch to plant into.