Pre-heat oven to 425 degrees F (215 degrees C).
Peel and chop potatoes into 1" to 2" chunks.
Fill a medium pot halfway with water and set it on medium heat. Add 1 tsp salt (reserving the rest) and baking soda to the water. Add the potato chunks to the pot. Boil for 6-8 minutes or until just slightly tender.
Meanwhile, add olive oil, remaining salt, and pepper in a bowl big enough to hold the potato chunks.
When the potatoes are done, drain and allow to sit in the pan for 1 minute to evaporate any remaining water.
Add potatoes to the bowl with the olive oil mixture. Toss to coat. The surface of the chunks should break up slightly and become rough.
Transfer potatoes to a baking sheet and spread out evenly. Do not crowd. Place the tray in the oven.
Allow the potatoes to brown for around 20 minutes. Gently flip the potatoes over. Bake for an additional 10-20 minutes until they are golden on the outside.
Remove from oven. Sprinkle with salt and rosemary, if desired. Serve immediately.