Preheat oven to 425°. (Depending on the type of your roasting pan, you may need to lightly grease it.)
Cut off and discarding leaves and stem off of the head of cauliflower.
Wash it and pat it dry.
Cut cauliflower into florets. (Smaller florets will cook faster and preferred for better roasting.)
Combine cauliflower florets with oil, salt, pepper, and garlic powder in a mixing bowl. Mix until all cauliflower is evenly seasoned.
Spread seasoned cauliflower in a baking sheet in one even layer and make sure the baking sheet is big enough not to crowd the vegetables.
Bake for 20-25 minutes, until golden brown. (Add a few minutes if you want the cauliflower softer or take away a few minutes if you want it to remain crunchier.)