Here, the fields is in plural, it is more than one field. "Rolling" is continuing, miles means long and stretch means extend. The carpet always packed in a roll, we have to stretch the carpet on the floor for installation. Your sample expression is very artistic, using the fields as it were packed in a roll, it is being stretched for miles long. Simply means that the fields are connected into one large field and possibly, the wind makes the field to wave, it looks like rolling (continue to roll for miles).

Hi Alex No, it's not a physical process. This is a word that describes what the fields (or the hills they are on) look like. They are 'undulating', on gently sloping hills, so that the fields look a bit like mid-ocean swell waves. It could also mean that the crops themselves appear to be gently swaying backwards and forwards in the wind, appearing to be rolling backwards and forwards.

I can see a picture that peasants have a great havest autumn