In a large bowl, combine the potatoes, oil and salt and pepper to taste and toss to coat. Transfer to a baking sheet and roast until tender and easily pierced with a fork, 20 to 25 minutes.
Meanwhile, combine the milk, garlic and onion powders and cayenne in a small slow cooker or pot. Add the cheese and heat on high if using a slow cooker (or over low heat if using a pot) until the cheese is melted, 15 to 20 minutes. Whisk to completely blend the mixture. Stir in three-quarters of the bacon and chives (reserve the remaining bacon and chives for garnish). Stir in the roasted potatoes and gently mix until completely coated with the cheese sauce. Top with the remaining bacon and chives. Serve hot with cocktail picks.