In a large bowl, stir together warm water, yeast, and sugar. Let stand until creamy, about 10 minutes. To the yeast mixture, add the oil, salt, and 2 cups flour. Stir in the remaining flour, 1/2 cup at a time, until the dough has pulled away from the sides of the bowl. Turn out onto a lightly floured surface, and knead until smooth and elastic, about 8 minutes. Lightly oil a large bowl, place the dough in the bowl, and turn to coat. Cover with a damp cloth, and let rise in a warm place until doubled in volume, about 1 hour. Deflate the dough, and turn it out onto a lightly floured surface. Divide the dough into 16 equal pieces, and form into round balls. Place on lightly greased baking sheets at least 2 inches apart. Cover the rolls with a damp cloth, and let rise until doubled in volume, about 40 minutes. Meanwhile, preheat oven to 400°F (200° C). Bake for 18 to 20 minutes in the preheated oven, or until golden brown.