Preheat the oven to 400 degrees. Line a baking sheet with foil, spray, and set aside.

In a medium bowl, combine the mustard, butter, garlic, parley, salt, and pepper. Once mixed, add potatoes and toss until all are coated. Add potatoes to the prepared baking sheet.

Roast the potatoes for 35-40 minutes, flipping halfway through until tender on the inside.