If you get a High Roller Godfather Goal in Loot Cases, you have no chance of making the goal if you are in the middle of a Turf War. It seems like you should be given the option of High Roller or Turf War. True there is a re-roll but if you use it and get the High Roller its like losing a turn. I feel like you should not be penalized due to your current level IMO.
As long as you have an open slot in your Goals page you'll still get the next day's Goal. Goals don't expire so even if you've already used up today's re-roll you can wait for that to refresh tomorrow.