Preheat your oven to 400°F (200°C). Line two large baking sheets with parchment paper for easy cleanup.
Wash and chop all the vegetables as described in the ingredients list. Try to cut them into uniform 2-inch pieces so they cook evenly.
In a large bowl, combine the Brussels sprouts, carrots, parsnips, and red onion wedges.
Drizzle the olive oil and honey (or maple syrup) over the vegetables. Sprinkle with the dried rosemary, dried thyme, salt, and black pepper.
Toss everything together until the vegetables are evenly coated with the oil and seasonings.
Spread the vegetables in a single layer on the prepared baking sheets. Do not overcrowd the pans, as this will cause the vegetables to steam instead of roast. Use two pans if necessary.
Roast for 20-25 minutes, then remove from the oven and stir the vegetables.
If using, sprinkle the toasted pecans or walnuts over the vegetables. Return to the oven and roast for another 10-15 minutes, or until the vegetables are tender, caramelized, and slightly crispy at the edges.
Remove from the oven and garnish with fresh parsley, if desired. Serve warm.
Notes
For the best flavor and texture, do not overcrowd the baking sheets. Using two pans is key to achieving crispy, caramelized edges.
If you have fresh rosemary and thyme, use about 1 tablespoon of fresh chopped herbs in place of the dried for even better flavor.
Cutting the vegetables into similar-sized pieces ensures they cook at the same rate.
You can prepare the vegetables a day ahead. Chop them and store in an airtight container in the refrigerator, then toss with oil and seasonings just before roasting.