Heat oven to 375° F. Cut the buns into 1-inch pieces and place on a baking sheet lined with parchment paper or aluminum foil. Drizzle with the butter, sprinkle with 1/2 teaspoon salt and the herbs, and toss. Bake, turning once, until crisp and golden, about 15 minutes.
Transfer the sheet of parchment or foil and croutons off the pan to a counter to cool. (You can store the croutons in a resealable plastic bag in the refrigerator for up to 5 days or in the freezer for up to 3 months.)