Cut the potatoes into 2-inch cubes. Add them to a large pot, cover them with cold water, and add salt. Bring them to a boil, cook for 10 minutes, drain and cool for 20 minutes. The potatoes will now be only partly cooked and should be completely dry before you roast them.
Preheat the oven to 400 degrees F.
Toss the potatoes with the oil and salt and pepper, to taste, and spread them in one layer on a baking sheet. Roast until crispy and cooked through, about 45 minutes.
While the potatoes are roasting, make the herb butter: Mix the softened butter with the parsley, sage, rosemary, and thyme and season it with salt and pepper, to taste.