Oris and angelica play a special role in gin and are known as fixatives. What this means is they help stabilise and lock in the other gin flavors. While you may not notice the taste of orris explicitly, you’ll be hard pressed to find a gin that doesn’t use this or angelica at least in some quantities. This botanical is usually extremely hard and needs crushing to the powder before its use. This means orris root is usually bought and used in powdered form
Try approx 0.5gm per litre.
Check out this link for some info on ratios and some recipe ideas.