Preheat your oven to 425°F (220°C). In a large bowl, combine the sweet potatoes, cauliflower, and Brussels sprouts with olive oil, balsamic vinegar, garlic powder, salt, and pepper. Toss until evenly coated.

Spread the vegetables in a single layer on a large, rimmed sheet pan. For an extra herbaceous note, scatter a few rosemary or thyme sprigs over the top.

Roast the vegetables for about 25-30 minutes, stirring halfway through for even browning. They should be tender with slightly charred edges.

Nestle the halloumi slices among the vegetables on the sheet pan and return to the oven for an additional 8-10 minutes. This gentle heat will warm the halloumi, enhancing its pillowy texture while leaving the edges crisp.

Remove from the oven and drizzle a bit more balsamic vinegar if desired. Serve immediately while the halloumi remains warm and irresistibly soft.