Crumble the yeast in a mixing bowl or dough bowl. Pour buttermilk, sugar, and salt into the yeast. Stir the mixture with a hand whisk until the yeast is dissolved. Add oil, oatmeal, and lentil flour and mix well. Add wheat flour little by little and knead until you have a smooth and elastic dough. Place a damp tea towel (or use a shower cap) over the bowl. Let the dough rise for two hours. Knock down the dough and take it out onto a floured board. Knead it lightly and roll it out thinly. Cut the dough into triangles. If you are using regular sausages, cut each into three, and if you are using sausage rolls, they can be used as they are. Place a sausage at the wide end of each piece of dough and roll the dough around the sausage. Start from the wide end. Place the sausage rolls on a baking sheet lined with baking paper. Allow them to rise again for about 30 minutes. Bake the risen sausage rolls at 210 degrees Celsius (410 degrees Fahrenheit) (fan oven) for about 10 minutes. Let the freshly baked sausage rolls cool on a wire rack.