Preheat the oven to 425 F.
It’s up to you whether you want to peel your potatoes or not: I like leaving the skin on, but feel free to peel them if you want. Cut them into fry-size pieces. (Again, use your judgement: if you like bigger wedges, that’s totally fine! Or you can cut them into thinner fries if you like.)
Arrange the fries in a single layer on two baking sheets and drizzle with olive oil to lightly coat. Sprinkle with the cayenne, salt, and pepper and divide the rosemary sprigs among the fries. Toss everything together with your hands to coat evenly.
Bake for 15 minutes on the upper and lower racks, then switch the trays (upper tray goes to lower rack and vice versa). Use a spatula to move the fries around so they brown evenly.
Bake for another 15 minutes or until brown and crisp around the edges. Season with additional salt and pepper and let cool slightly.