I do of work all over Denver and Colorado Springs . I'm up there a few weeks a month. You really don't need to do anything different. The winters aren't too bad. It does get cold but the roads are very well taken care of. I always have rental cars and they never put snow tires or anything in them. I typically get mid level cars like a Focus or Carolla. They do fine. It's when you are driving to the western slope like Vail or Grand Junction that can get dicey.
I wouldn't get winter tires either. The winter is kind of nuts. One day its snowy and 20 degrees, the next its 70 and sunny. This happens pretty much Nov-May. More often than not its pretty sunny.