Preheat oven to 425°F. Toss potatoes, sausage, corn, and bell pepper with 2 tablespoons olive oil and 1 tablespoon Cajun seasoning on a large sheet pan.
Roast for 12 minutes until potatoes start to soften.
Meanwhile, toss shrimp with remaining olive oil, Cajun seasoning, and minced garlic in a bowl.
Remove pan from oven, add shrimp, and drizzle everything with melted butter. Return to oven for 5-6 minutes until shrimp are pink and cooked through.
Squeeze fresh lemon juice over everything, garnish with parsley, and serve with extra lemon wedges. Delicious over rice or with crusty bread!