If this were up to me, I would approach this in the following manner. First and foremost, I would want to use that free rye seed, that said, it has to be mature before doing any of the other steps or you risk it not germinating properly. Since you are planning on using rutabagas, and they are a long season brassica(average about 90 days to maturity), time is of the essence if you also want those to mature before your first frost date, which I assume is pretty early given the locations you have listed. As soon as the rye is mature(maybe that is right now), and if you think you need(or want) to spray for weeds, hit the whole field with a dose of gly. If it is not weedy, save your herbicide. Then you need to broadcast the rutabaga seed at 1.5 to 2 lbs per acre, followed by either mowing the rye or rolling it down. To be honest, I would do both(but I like seat time on the tractor), mowing will "spread" the rye seed more evenly than rolling alone, but I would also want the benefit of the added seed to soil contact provided by rolling it with a cultipacker. Obviously doing all those steps seems a bit redundant to some extent, but none of it will make your crop any less likely to succeed, and will potentially help in the long run. Lots of other good suggestions here as well, and this is just one way to do it. I do like mikmaze's suggestions of adding some clover, but I would not add crimson in your location, I would be more inclined to add some medium or mammoth red clover instead. Good luck and keep us posted!