Begin by preheating your oven to 425°F. Prepare a large, rimmed baking sheet by lining it with parchment paper and give it a light coating of olive oil spray to prevent sticking.
Clean the cauliflower heads under water. Carefully remove the outer leaves and trim the stem end. You need to ensure the core remains intact to hold the steaks together. Cut the cauliflower into 3/4-inch-thick steaks. You can expect to get about three good steaks from each head (you can roast the smaller pieces alongside the steaks).
Place the cauliflower steaks and any florets onto the prepared baking sheet in a single layer, ensuring they’re not overcrowded. Mist the tops with olive oil spray and evenly distribute half of the combined seasonings over them.
Roast the cauliflower in the preheated oven for 15 minutes. After this initial cooking time, carefully flip the steaks and florets. Give them another spray of olive oil and finish with the rest of the seasonings.