In a blender, combine sage, pine nuts, olive oil, garlic, Parmesan, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Puree until smooth.
Season turkey all over with salt and black pepper and transfer to prepared pan. Spread pesto all over top of turkey. Arrange potatoes around turkey in pan, spray with cooking spray and season with salt and freshly ground black pepper.
Roast for 30 minutes, until potatoes are golden brown and turkey reaches 160 degrees F. Let turkey rest for 10 minutes before slicing crosswise into 1/2-inch thick slices. Serve half of the turkey with all of potatoes. Reserve remaining turkey for salad, if desired