In a large bowl or in the bowl of a heavy-duty electric mixer, sprinkle the yeast over the water and stir. Let stand until the yeast softens, about 10 minutes. Stir to dissolve the yeast.
Using a wooden spoon or the paddle blade of the mixer, stir in the oil, salt and pepper. Gradually beat in enough flour to make a shaggy dough that clears the sides of the bowl.
If kneading by hand, turn out the dough onto a lightly floured work surface. Knead the dough, adding more flour as needed, until the dough is smooth and elastic, about 10 minutes.
If kneading by machine, change to the dough hook and knead on medium-low speed until the dough is smooth and elastic, about 8 minutes. If desired, knead on the work surface to check the consistency.
Shape the dough into a ball. Transfer the dough to a lightly oiled large bowl. Turn to coat the dough with oil. Cover tightly with plastic wrap. Let stand in a warm place until doubled in volume, about 1 hour.
Punch down the dough and shape into a ball. Return the dough to the bowl, turn to coat with oil, cover and let rise until doubled again, about 45 minutes.
Position a rack in the center of the oven and preheat to 400 degrees F. Lightly oil a large baking sheet.
Turn out the dough onto the work surface. Knead, gradually working in the prosciutto and rosemary. Flatten the dough into a 12-inch disk. Starting at a long end, roll up jelly-roll style. Pinch the seams shut. Place on a baking sheet, seam side down. Cover loosely with plastic wrap. Let rise until doubled in volume, about 30 minutes.
Using a very sharp knife, cut 3 shallow diagonal slashes in the top of the bread. Bake until the bread is golden brown and sounds hollow when tapped on the bottom, 35 to 40 minutes. Cool completely on a wire rack. If desired, wrap in aluminum foil and store at room temperature up to 8 hours before serving.
The bread is best served the day baked.
Copyright Rick Rodgers, Christmas 101, Random House, 1999