Make the Cajun Butter: In a small pot, melt the butter over medium heat. Stir in the chile powder, paprika, garlic powder, black pepper, thyme, oregano, cayenne pepper and red-pepper flakes; heat for 30 seconds to 1 minute. Set aside.
Cook the Potatoes: Put the potatoes in a medium pot and add enough water to cover by 1 inch. Bring to a boil and cook until just barely fork tender, 7 to 8 minutes. Drain.
Assemble the Skewers: Arrange 3 shrimp, 3 pieces of sausage, 3 potatoes and 2 pieces of corn on each skewer.
Brush each skewer generously with the Cajun butter and season with salt and pepper. Working in batches, cook on a preheated grill or grill pan until nicely charred on both sides, 4 to 5 minutes per side.
Serve immediately, garnished with parsley and lemon wedges.