Cut the cauliflower into florets and toss with a bit of oil, salt and pepper. Put the florets into a roasting pan that can hold them in a single layer. Sprinkle some lemon juice over the cauliflower.
Roast about 20-25 minutes, turning the cauliflower every 10 minutes or so, until lightly browned and cooked through. Poke them with a fork to test for doneness.
Sprinkle with grated Parmesan if you'd like and serve.