Start by preheating your oven to 400°F. While it heats, prepare all your vegetables: cut the sweet potatoes and carrots into 1-inch pieces, break the cauliflower into 1-inch florets, and cut the red onion into 1-inch chunks. Having everything prepped and ready before you start cooking (mise en place) ensures the roasting process goes smoothly without interruption. Spread the prepared vegetables evenly on a large sheet pan.

In a small bowl, whisk together the olive oil and harissa until well combined. This mixture creates the flavor base and helps the spices adhere to the vegetables. Pour the harissa-oil mixture over the prepared vegetables and toss everything together thoroughly, making sure each piece gets coated. Don't be shy with the tossing—good coverage ensures even browning and consistent flavor throughout.

In a separate small bowl, combine all the dry spices: salt, black pepper, garlic powder, cumin, paprika, and smoked paprika. Mix them together so they're evenly distributed, then sprinkle this blend over the harissa-coated vegetables. Toss everything one final time until the spices are evenly distributed throughout. I like to do a final taste check by trying a small piece of raw vegetable with the coating to ensure the seasoning balance is right before roasting.

Transfer the seasoned vegetables to the preheated 400°F oven and roast for 30 minutes. After 30 minutes, carefully stir and flip the vegetables to promote even browning on all sides, paying special attention to vegetables on the edges which brown faster. Return to the oven for another 25-30 minutes, until the vegetables are tender when pierced with a fork and the edges begin to caramelize and turn golden brown.

Once the vegetables are tender and golden, switch your oven to the broil setting and place the pan on the upper rack. Broil for 2-3 minutes, watching carefully so the vegetables caramelize and the edges crisp up without burning. The high, direct heat from the broiler creates those appealing charred spots and intensifies the roasted flavor. Remove from the oven immediately once the tops look crispy and caramelized.

Transfer the harissa roasted vegetables to a serving platter or individual plates while they're still warm. The vegetables are best enjoyed immediately while the textures are still crispy on the outside and tender inside. Serve as a side dish, over grain bowls, or alongside roasted proteins.