Preheat oven to 400°. Line a large, rimmed baking sheet with parchment paper or foil.
In a small bowl, crush rosemary and salt together between your fingers so that the rosemary needles are broken up. Use a mortar and pestle if you have one. Put chickpeas in a medium bowl and add olive oil, salt and rosemary mixture. Toss until chickpeas are well coated.
Put chickpeas in a single layer on baking sheet. Bake for 25 minutes, occasionally shaking pan to make sure chickpeas roast evenly. When done they should be golden brown and crunchy.
Remove from oven and let cool before handling, about 10 minutes. Serve warm or at room temperature; these are best eaten the same day. Store in a covered container at room temperature for up to 3 days.