Suprised you didn't choose another grain as an example, Barley_Man. :)
Oats have been grown and eaten by families in Scotland for centuries and there's plenty of established ways to deal with it. John Gerard's Great Herball, or, Generall Historie of Plantes (1597) discusses the selection process for hulless oat varieties. For hulled oats, there are a variety of mechanical ways to deal with it and/or you can heat the groats up in the oven to crack the outer husk before winnowing.
Rolled oats can be made at home using the traditional method of simply soaking then steaming and rolling them in a grain mill before drying. You can get a hand-cranked grain mill for AU$300 that can also make flakes and flours of most grains or legumes. Those prices are for fancy brand equipment for people who are into making their own flour and flakes as a hobby, but in a widespread, ongoing food security crisis, equipment to make a variety of food more edible would probably become more of a commodity item itself.