Preheat the oven to 425°F (220°C).
Wash the mini potatoes thoroughly and pat them dry. Place each potato on a cutting board and make several thin slices across the top, being careful not to cut all the way through (about 3/4 of the way down).
Arrange the potatoes on a baking sheet. Drizzle with olive oil and sprinkle with salt, black pepper, garlic powder, onion powder, and smoked paprika. Toss to coat evenly.
Roast the potatoes in the preheated oven for 25-30 minutes, or until they are tender and crispy on the edges. You can check for doneness by inserting a fork into one of the potatoes.
While the potatoes are roasting, prepare the Cajun dip. In a small bowl, combine sour cream, mayonnaise, Cajun seasoning, and lemon juice. Mix well until smooth and creamy.
Once the potatoes are done, remove them from the oven and let them cool slightly. Serve warm with the Cajun dip on the side, garnished with chopped parsley.