Preheat your oven to 425°F for 10 minutes while you prepare the vegetables. Line a large sheet pan (about 18x13 inches) with parchment paper or lightly brush it with oil.

Wash all vegetables thoroughly. Cut baby carrots in half lengthwise, halve Brussels sprouts, quarter baby potatoes into roughly 1-inch pieces, leave cherry tomatoes whole, cut bell peppers into 1-inch chunks, cut red onion into 1-inch wedges, and halve mushrooms. Aim for similar sizes so everything cooks evenly — about 2–5 minutes total cutting time.

Checkpoint: You are ready to move on when all vegetables are cut into similar sizes.

Place all cut vegetables in a large mixing bowl. Add 5 tablespoons olive oil, 2 teaspoons Italian herbs, 1 teaspoon thyme, 1 teaspoon garlic powder, 0.5 teaspoon smoked paprika, and salt and black pepper to taste — about 0.5 teaspoon each to start.

Using a large spoon or your hands, toss everything together for 1–2 minutes until all vegetables are evenly coated with oil and seasonings look distributed throughout. Every piece should glisten slightly.

Checkpoint: You are ready to move on when all vegetables appear evenly coated with oil and seasonings are no longer clumpy.

Spread the coated vegetables in a single layer on your prepared sheet pan. Try to place larger pieces like Brussels sprouts and potatoes cut-side down first, as this helps them caramelize. Don't crowd the pan — if needed, use two pans. Vegetables should be in mostly one layer with minimal overlap.

Place the sheet pan on the middle oven rack and roast at 425°F for 15 minutes without stirring. After 15 minutes, use a large spoon to stir and flip the vegetables so they brown evenly on all sides — about 1–2 minutes.

Return to oven and roast for another 10–15 minutes until vegetables are fork-tender inside and edges are deeply golden brown (some caramelized spots are perfect). The Brussels sprouts and potatoes should be the doneness indicator — they're done when a fork pierces them easily.

Checkpoint: You are ready to move on when vegetables are tender and have golden-brown or lightly caramelized edges.

Remove the sheet pan from the oven and immediately drizzle 2 tablespoons balsamic vinegar evenly over all vegetables — about 5 seconds. Toss gently with a spoon for 1 minute, letting the vinegar coat everything and sizzle slightly from the residual heat.

Transfer vegetables to a serving dish or platter using a spatula. Sprinkle 1 tablespoon chopped fresh parsley and 0.25 cup grated Parmesan cheese over the top. Serve immediately while still warm.

Troubleshooting Tips:If vegetables aren't browning enough at the 15-minute mark, they may be too crowded or cut too large — spread them further apart for remaining cook time.

If potatoes are still hard after 25 minutes, cut them into smaller pieces next time or start them 5 minutes before adding other vegetables.

If edges are burning but centers are soft, lower oven temperature to 400°F and add 5 minutes cooking time.

If vegetables are too watery, pat them dry with paper towels before tossing with oil — excess moisture prevents caramelization.

If balsamic vinegar makes vegetables soggy, add it just before serving rather than mixing it in early.