Heat oil in a non-stick skillet over medium-high heat. Add potatoes and stir to coat. Cook for 4-5 minutes, until potatoes have begun to absorb oil. Stir in rosemary.
Reduce heat to medium-low, cover, and cook for about 30 minutes or until potatoes yield to a fork. It's best if the potatoes are in a single layer in the skillet. Feel free to peek, and to stir occasionally.
Uncover and increase heat to medium-high again. Cook, stirring frequently, until potatoes reach desired level of crispiness.