Preheat oven to 400°F. Cut cauliflower into florets and put in a single layer on large baking pan. Drizzle olive oil over top and sprinkle with rosemary and salt. Toss it around with your hands.
When oven is preheated, place pan in oven for 25 minutes. Toss around with spatula and then sprinkle with bread crumbs. Cook for another 5-10 minutes until golden brown and delicious.