Season roast all over with kosher salt while it comes to room temp (this is especially important with large cuts of meat). The salt will draw out liquid from the roast, so it's best to place the roast on a wire rack set inside a large (but not too large) roasting pan (this setup will keep the meat from sitting directly in the liquid and allow the roast to cook more evenly later). Let sit at room temperature at least 2 hours before putting in the oven.
Meanwhile, chop anchovies and 2 rosemary/thyme sprigs. Transfer to a small bowl and add garlic and 1/4 cup olive oil. Mix well to combine and season with salt and pepper. It's the anchovy oil rub that gives this roast the most delicious umami crust.
Preheat oven to 250° on Roast setting. (This is the low and slow part). If your oven doesn’t have Roast, use Bake.
Remove any liquid that formed in the bottom of the pan and then place remaining rosemary/thyme sprigs on the bottom of the roasting pan. Next, smear anchovy oil mixture all over. Roast until an instant-read thermometer inserted into the thickest part registers 110°, approx. 2 1/2 hours for medium-rare (temperature will rise as it sits; it should eventually hit 125°). Remove from oven and let rest for at least 30 minutes.
While meat is resting, combine parsley and remaining 1/4 cup olive oil.
About 20 minutes before you want to eat, increase oven temperature to 500°. (This is the high-heat, quick searing part.) Roast meat in the same roasting pan until the fat is golden brown, 10–15 minutes. (I roasted mine for 10 minutes). Tip: to reduce oven smoking, add 1/4 water to the bottom of the pan. Transfer roast to a cutting board, leaving any pan juices behind.
Cut bones away from rib roast (you can separate bones and crisp up in the oven or serve them as they are). Then slice meat to your preferred thickness. Arrange sliced meat and rib bones on a platter and pour parsley oil mixture over. Sprinkle with sea salt and more parsley, if desired.
Do Ahead: Meat can be low and slow roasted 2 hours ahead. Store loosely covered with foil at room temperature. And then finish with the high heat 20 minutes before you're ready to serve.