Preheat the oven: Set it to 425°F (220°C).
Place two large sheet pans inside while the oven heats. Hot pans help the vegetables brown better.
Prep the vegetables: Wash, dry well, and cut everything into even, bite-sized pieces. Keep firmer vegetables (carrots, Brussels sprouts) slightly smaller than softer ones (zucchini) so they finish at the same time.
Make the lemon-garlic mixture: In a large bowl, whisk olive oil, lemon zest, lemon juice, garlic, salt, pepper, red pepper flakes, and dried oregano.
Taste and adjust the salt.
Toss to coat: Add the vegetables to the bowl and toss until everything is lightly coated. You want a thin sheen of oil, not a puddle.
Arrange on hot pans: Carefully remove the pans from the oven. Spread the vegetables into a single layer with space between pieces.
Crowding causes steaming instead of roasting.
Roast and rotate: Roast for 15 minutes. Stir and rotate the pans top-to-bottom and front-to-back for even color.
Finish roasting: Continue for 10–15 minutes more, until edges are browned and centers are tender. Cherry tomatoes and asparagus may finish sooner; pull them early if needed.
Brighten and serve: Toss with a little more lemon juice, sprinkle with fresh herbs, and adjust salt.
Add Parmesan, capers, or a light drizzle of balsamic if you like. Serve hot or warm.