Preheat oven to 250°F.
In a bowl (or in the pretzel bag itself) toss the pretzels gently with the melted butter to coat evenly.
Sprinkle the ranch dressing mix over the pretzels and again toss to coat evenly.
Arrange the pretzels in a single layer on a half sheet pan and bake for 30 to 45 minutes, stirring every 15 minutes, or until the pretzels are dry to the touch and the seasoning is set on them.
Eat warm, or let cool completely to room temperature before transferring to an airtight container or bag for storage.
These are good for about a week at room temperature.