Grass loses its nutritional content later in the year and when it is frosted, so although grazing will give the sheep something to keep their jaws happy, they won't be getting much feed from it. This is fine for non-breeding animals of some breeds, but certainly breeding ewes will need something more than that. I can really only tell you what we do for our Hebrideans, at 1000' in southern Scotland, where we can expect seriously below zero temps from Oct onwards, and several weeks of deep snow (our sheep can scrape it away to a depth of about 8-9" but no deeper). We start putting ad lib hay out in late Oct, or earlier if we judge the weather is severe, and continue until we have grass growth again in April. Sometimes we have a couple of weeks of grass growth in Feb but that is just an extra treat for the sheep. As well as hay, our sheep have a 'Crystalix' type bucket over the winter, and are fed a general coarse mix - the primitives don't need the high protein feeds available such as ewe pencils and can't really get their mouths around big rolls, and all that protein can make them scour. High protein feeds would be appropriate for your breed, on an increasing dose from 6 weeks before they are expected to start lambing. In addition, we feed willow and ash branches for extra vitamins and trace elements, as well as the fun for the sheep of stripping the bark.