Preheat your oven to 425°F (220°C) and line a large sheet pan with parchment paper for easy cleanup.
In a large bowl, toss the cubed red potatoes and chopped yellow onions with the olive oil, seasoned salt, and black pepper until they are evenly coated.
Spread the potato and onion mixture in a single layer on the prepared sheet pan. Roast for 60 to 75 minutes, flipping halfway through until golden brown and crispy.
Let the potatoes and onions cool for about 15 minutes after roasting.
Whisk together the sour cream, mayonnaise, paprika, and black pepper in a medium bowl until smooth and creamy.
Gently fold the roasted potatoes and onions into the creamy dressing until well coated.
Garnish with chopped fresh chives before serving.
Notes
For added flavor, consider adding garlic powder or fresh herbs to the vegetable mixture before roasting.