Preheat the oven to 400 degrees Fahrenheit.
Chop the potatoes in half lengthwise.
Add to a colander and run until water until clean.
Add to a large mixing bowl and toss with olive oil.
Finely mince the garlic and add to the bowl.
Add all remaining ingredients aside from the rosemary.
Add to a cast iron skillet
or regular baking sheet.
Keeping the rosemary in about 5 small bunches (attached to the stem should be smaller bunches) add it to the top of the potatoes, spread throughout.
Bake uncovered for 20-35 minutes or until easily pierced with a fork. Cook time can vary because fingerling potatoes can vary in size quite a bit, so check after 20 minutes by poking with a fork.
Remove from the oven and serve warm.