Any roast (dark, medium, or light/blonde) can be used to make an Iced Americano as long as the drink is made with espresso. Use an espresso machine or a Nespresso.
Use Nespresso Starbucks espresso capsules to make the drink taste more like the one at Starbucks.
If you'd like to sweeten your Iced Americano, use simple syrup instead of granulated sugar so that it dissolves well when mixed. You can even try a flavored syrup, like brown sugar or vanilla syrups.
Make the espresso fresh for the best flavor. The cold water will instantly cool the hot espresso.
You can adjust the amount of espresso and water in your Iced Americano, depending on how strong you want the flavor and caffeine to be.