Preheat the oven to 400°F (200°C).
Wash and cut baby potatoes in half or quarters.
Slice smoked sausage into 1/4-inch thick rounds.
In a small bowl, mix ranch seasoning, garlic powder, onion powder, and black pepper.
In a large bowl, toss potatoes with olive oil and half the seasoning mixture.
Line a baking sheet with parchment paper or grease lightly.
Spread seasoned potatoes evenly on the baking sheet.
Scatter sliced sausage evenly over the potatoes.
Roast in the oven for 35-40 minutes, stirring halfway through.
Remove from oven and sprinkle shredded cheddar cheese over the potatoes and sausage.
Return to oven and bake for an additional 5 minutes until cheese is melted and bubbly.
Garnish with chopped fresh parsley and serve hot with sour cream if desired.