Wash and peel the potatoes, then cut them into 2 inch chunks.
Add the potatoes to a large pot or dutch oven. Fill with 5 quarts of water or until the potatoes are completely covered. Add the kosher salt and baking soda then mix until dissolved. Bring the water to a boil over high heat and boil the potatoes for 15-20 minutes until fork tender.
Add in a nonstick baking sheet and preheat the oven to 425F. If possible, use the roast or convection setting.
Once the potatoes are fork tender, drain them and place them back in the pot. Shake them until they become rough and textured around the edges.
Add the potatoes to a large bowl, then season with 2 tbsp duck fat, dried rosemary, garlic powder, onion powder, black pepper and the remaining kosher salt. Add them to the potatoes and mix to combine, further roughing them around the edges.
Once the roasting pan is preheated, take out the pan place it on a heat resistant surface. Add the duck fat then carefully place the potatoes on the pan and toss them in the fat until fully covered and in a single layer. Bake at 425F for 50-60 minutes until a deep golden brown, flipping every 20-30 minutes for extra crispy potatoes.
Notes
I like using Russet potatoes for making Roasted Potatoes, as they are more starchy, which results in a beautiful crust with fluffy insides. Yukon Gold potatoes, which are another one of my preferred potatoes, are more creamy - which makes for softer roasted potatoes. You can use either one to great success - it really depends on what you prefer (or have on hand).
Baking soda is one of my secret ingredients to the best roasted potatoes! It helps break down the potatoes surface and pectin - this draws the starches to the surface of the potatoes, which helps them brown and become crispy!
Duck fat is my favorite oil/fat to roast potatoes in - it adds a layer of flavor that cannot be beat! If you have access to it but have never tried it, I strongly urge you to try - I promise it takes the potatoes to another level! However, I know this may not be available to everyone. You can use rendered chicken fat or substitute with a neutral oil (my recommendation is avocado oil).
If you are scaling this recipe, scale the 2 tbsp of duck fat according to the weight of potatoes. (ie. only double the fat if you are doubling the weight of your potatoes) There's no need to use more the 1/2 cup duck fat for a full size baking sheet.
After you've boiled the potatoes, drain them and then place them back in the pot and shake them until they look rough and textured around the edges. Once coated in duck fat (or avocado oil), the rough textures will develop a beautiful crispy crust as they roast in the oven.