Preheat the oven to 425℉. Line a sheet pan with parchment paper.
Drain rinsed chickpeas on a paper towel and let them dry for about 30 minutes. Get as much moisture off the surface as possible for a crunchier snack.
Place dried chickpeas in a bowl and toss with the olive oil, rosemary, and sea salt.
Pour onto the prepared sheet pan and spread out. Place the pan in the middle of the preheated oven and cook, tossing partway through, for 30 minutes until slightly browned and crispy.
Remove from the oven and allow to cool completely. Store in a resealable container until you are ready to use it.