Preheat the oven to 400F.
Add sliced smoked sausages to the large bowl.
Cut red onion, bell pepper, and potatoes into the size you want. Add to the bowl with sliced smoked sausages.
In a small bowl, mix together the seasonings (smoked paprika, red pepper flakes, salt, and freshly ground black pepper). Sprinkle over the veggies and sausages. Drizzle with olive oil and toss to coat completely.
Line a baking sheet with aluminum foil or parchment paper. Transfer sausage, bell peppers, onion, and potatoes to the prepared baking sheet. Bake in the preheated oven for 20 minutes. Then, remove from the oven. Add minced garlic and dried thyme, stir together. Return to the oven and bake for 15-20 minutes or until golden brown and ready. Remove from the oven and top with shredded white cheddar cheese. Bake for additional 2-3 minutes or until the cheese melts. Garnish with fresh thyme or chopped flat-leaf/curly parsley. Serve warm.