I think when Winder is ready, and he appears to be close, he will be long relief, and/or relief in some capacity. It was the role he was going to fill last season until we had too many injuries to our starting rotation. And given his shoulder/injury issues, I don't see him destined to be a starter at this point. But ... this is just my opinion and based on nothing but it's just what I think will be.
As for Ober, Varland and RSW, they will get their opportunities to start, either injury replacement or as an occasional 6th starter to give the rotation an extra day here and there. And, I see that Sunday's game, the pitcher is listed as 'tbd', and that would be Ober's day to start in St. Paul (I think), will be be inserted there? Of course, some of this will depend on Maeda, if he winds up on the IL or if they will wait and see.
IF Maeda goes on the IL, I think Ober is up in his place. Headrick I think gets swapped out for Winder or Sands, and that will likely be the rotation there between the Twins BP and AAA.