Heat oven to 425°F. Place a large sheet pan inside to preheat.
Cut potatoes, carrots, bell pepper, and onion as directed. Break broccoli into bite-size florets.
Whisk olive oil, garlic, salt, pepper, Italian seasoning, smoked paprika, and lemon zest in a large bowl.
Toss potatoes and carrots with half the garlic oil. Spread on the hot pan in an even layer.
Roast 15 minutes, stirring once halfway, until edges start to color.
Coat broccoli, bell pepper, and onion with the remaining oil. Add to pan, toss, and spread out.
Roast 18–22 minutes more, until tender and nicely browned in spots.
Drizzle with lemon juice, sprinkle parsley, and toss. Taste and adjust seasoning. Serve hot.