1. For the deviled sauce: In a blender, combine, butter, roasted onion, chipotle chile, guajillo chile, árbol chile, garlic, ketchup, lime juice, salt and pepper. Blend until smooth and set aside.
2. For the garlic parsley butter: In a bowl, mix melted butter, parsley, and garlic. Set aside.
3. Thread shrimp onto skewers. Brush with deviled sauce and set aside.
4. Preheat grill 45 minutes before using. Once hot, grill shrimp skewers over direct heat for 3 minutes per side. Brush with garlic parsley butter and set aside.
5. Serve deviled shrimp skewers with guacamole and lemon wedges on the side.