Add yeast, sugar and water in a mixing bowl. Let the yeast rise in bowl until bubbly. Add the oil, rosemary, salt and flour and knead together until smooth and slightly sticky. This usually takes 10 minutes on medium speed. Roll dough into two large round loaves, or four small loaves. Place the round loaves of dough on a greased cookie sheet. Let the bread rise until they double in size, about 30-40 minutes. Bake at 400 for 15-20 minutes, or until top is golden brown. Melt butter and spread over the baked loaves and sprinkle with coarse salt.