Pile the cauliflower, lemon and garlic into the middle of a heavy baking sheet.
Drizzle the olive oil over and stir to get everything coated.
Spread the vegetables and lemon in an even layer on the pan, and sprinkle with the salt and pepper.
Place the pan in the oven for 20 minutes, stir the vegetable mixture and spread back out on the pan.
Return the pan to the oven and roast another 10 minutes. Test for doneness [you are looking for a tender-crisp texture], and return to the oven if the cauliflower isn't quite as done as you like it.
Scrape everything into a serving bowl and stir to blend the flavors and get the lemon flavor on every piece of cauliflower. Serve immediately - store leftovers in the fridge
Notes
Cauliflower already cut into florets will fine and it's a time-saver.If you're in a hurry, cut the cauliflower into smaller pieces, which will cook more quickly.