Preheat oven to 220 degrees C. Spray a shallow 23 cm square tin with vegetable oil cooking spray.
To prepare filling, combine brown sugar, walnuts and cinnamon in a small bowl. Mix well.
In a large bowl, sift flour, add white sugar, raisins, baking powder, bicarbonate of soda and salt. Stir well. Add yoghurt and oil, stir until a dough forms. On a lightly floured surface, knead dough 8 - 10 times. Roll dough into a 25 x 30 cm rectangle.
Brush dough with margarine, sprinkle filling over dough. Starting with a long edge, roll dough. Starting with a long edge, roll dough Swiss-roll style into a log. Pinch seam to seal. Cut into twelve 2.5 cm slices. Place rolls, cut side up, slightly touching , in three rows in prepared tin.
Bake until lightly golden, 15-17 minutes. Cool for 10 minutes, then turn out. Serve warm.