Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.
Wash potatoes and pat them dry with paper towels. Cut into even 1-inch cubes.
In a large bowl, toss potato cubes with olive oil, salt, black pepper, and smoked paprika until evenly coated.
Spread potatoes in a single layer on the prepared baking sheet, ensuring they're not overcrowded.
Roast for 25-30 minutes, flipping halfway through, until potatoes are golden brown and crispy on the outside.
While potatoes roast, prepare the dressing by whisking together mayonnaise, Dijon mustard, apple cider vinegar, dill, and a pinch of salt in a small bowl.
Remove potatoes from the oven and let cool for 5-10 minutes.
Transfer the potatoes to a large serving bowl and gently fold in the dressing until evenly coated.
Add chopped green onions and any optional ingredients, folding gently to maintain the crispy texture of the potatoes.
Let the salad rest for about 15 minutes before serving warm or at room temperature to allow flavors to develop.