Place the potatoes in a stockpot and cover with cold water; add the rosemary and garlic. Bring to a simmer and cook until the potatoes are al dente, about 30 minutes. Remove the potatoes from the water and let cool.
Preheat a deep-fryer filled with vegetable oil to 350 degrees F.
Cut the potatoes into bite-size pieces and fry them in the oil until golden brown and crispy. Drain on paper towels, then transfer to a bowl and season with salt and pepper.