Heat oven to 450°F (230°C). Line a rimmed sheet pan with parchment for easy cleanup. Place the pan in the oven to preheat for extra browning—yes, the pan gets hot on purpose.
Toss baby potatoes with 1 tablespoon olive oil, salt, and pepper. Carefully spread onto the hot pan. Roast 12–15 minutes until edges start to brown.
In a bowl, combine melted butter, remaining 2 tablespoons olive oil, minced garlic, lemon zest, lemon juice, smoked paprika, red pepper flakes, oregano, 1 teaspoon salt, and 1/2 teaspoon pepper. Whisk. Smell that? That's winning.
Pat shrimp very dry. Toss with 2–3 tablespoons of the lemon-garlic mixture. Reserve the rest for finishing and veggies.
Pull the pan out. Add bell pepper, red onion, and cherry tomatoes to the potatoes. Drizzle with half of the remaining lemon-garlic mixture. Toss right on the pan. Roast 8 minutes.
Scoot veg to the edges, spread shrimp in a single layer in the center. Roast 5–7 minutes until shrimp are pink and just curled (C-shape, not O-shape).
Remove from oven, drizzle remaining lemon-garlic butter over everything. Sprinkle parsley. Taste and adjust salt, pepper, and lemon.
Plate as-is for a low-carb win, or serve over rice, orzo, quinoa, or garlicky toast to mop the juices. Finish with extra lemon wedges because you're classy like that.