Preheat the oven and prep the pan. Heat to 425°F (220°C).
Line a large sheet pan with parchment for easy cleanup, or lightly oil it.
Make the lemon-garlic mixture. In a bowl, combine lemon zest and juice, minced garlic, olive oil, melted butter, honey (if using), red pepper flakes, paprika, salt, and black pepper. Stir until well mixed.
Toss the vegetables. Add the asparagus, bell pepper, and red onion to the pan. Spoon over about one-third of the lemon-garlic mixture.
Toss directly on the pan to coat, spreading in an even layer.
Start roasting the veggies. Roast for 10 minutes to give them a head start. This helps them caramelize and stay tender-crisp.
Prep the shrimp. While the vegetables roast, pat the shrimp dry with paper towels. Toss the shrimp with the remaining lemon-garlic mixture in a bowl until coated.
Add the shrimp. Pull the pan out, push the vegetables to the sides, and spread the shrimp in a single layer in the center.
Avoid crowding so they sear instead of steam.
Roast until just cooked. Return the pan to the oven and roast for 6–8 minutes, or until the shrimp are pink, opaque, and slightly curled. Do not overcook.
Finish and serve. Sprinkle with chopped parsley and a pinch more salt if needed. Serve with lemon wedges.
Pair with rice, quinoa, pasta, or bread to soak up the juices.