Preheat the oven to 300 degrees F and line a baking sheet with parchment paper.
Place the butter and honey in a small saucepan over medium heat and cook until the butter is melted, about 3 minutes. Stir in the rosemary and salt.
Combine the cereal and crackers in a large bowl. Pour over the melted butter and toss well to coat, then pour the snack mix onto the prepared baking sheet. Bake on the center rack, stirring once or twice during baking, until the snack mix is toasted and fragrant, about 40 minutes. Allow to cool before storing in an airtight container.