In a small bowl, combine the yeast, sugar, and warm water and stir to mix. Let stand until foamy, about 5 minutes. In a large bowl, stir together the flour and the rosemary. In a food processor, combine the yeast mixture, half of the flour mixture, 1 tablespoon of the oil, and the salt. Process 1 to 2 minutes to mix well, then add the remaining flour mixture and process Until a ball forms, about 1 minute.

Remove to a lightly floured work surface and knead until the dough is smooth and elastic, 6 or 7 minutes, adding the walnuts after 4 or 5 minutes. Gather into a ball. Oil a bowl with 1 tablespoon of the oil, put the ball of dough in the bowl, and turn to coat with the oil. Cover the bowl with a damp kitchen towel, put in a warm place, and let the dough rise until nearly doubled in size, about 1 hour.

Pinch down the dough in the bowl, cover with the towel again, and let rise until nearly double in size, another 15 minutes. Meanwhile, preheat an oven to 450°F.

Divide the dough into 3 equal balls. Oil a lightly floured work surface, roll out each ball into a round 12 inches in diameter and a scant 1/4 inch thick. Place each round on a baking sheet, and brush the tops with the remaining 1 tablespoon oil. Slip 2 baking sheets onto the middle oven racks and bake until golden and cooked through, 12 to 15 minutes. Remove from oven and bake the remaining round. Serve hot, warm, or at room temperature.

MAKES THREE 12-ROUNDS; EACH ROUND SERVES 6 TO 8