Rinse the potatoes under cold water, and dry with a kitchen towel. Then, cut the potatoes into halves or quarters, depending on the size of the potatoes.
Place the cut potatoes in a large mixing bowl and toss them with melted butter, olive oil, chopped rosemary, salt, and pepper.
Spread the seasoned potatoes evenly on the baking sheet, making sure that they are spaced out and not overlapping.
Roast the potatoes for 15 minutes, and then take them out and flip them over.
Roast for another 10 to 15 minutes, or until the potatoes are crispy, golden-brown, and tender. If necessary, turn the potatoes again and continue roasting until done.
Remove the potatoes from the oven, and sprinkle with chopped parsley and Parmesan.
Cool for a few minutes before serving with the yogurt sauce, if using.
For the Yogurt Sauce
Combine all ingredients in a bowl and whisk until thoroughly combined.
Keep refrigerated until ready to use.
Notes
Cut the potatoes into halves or quarters, but most importantly, you want even, bite-sized pieces.
Swap half the potatoes with carrots for a different flavor and texture.
If you don't like rosemary, you can use your favorite fresh (or dried) herbs.