Coriander roots have a different flavour to the coriander leaves and are often used in Asian recipes. If the recipe calls for coriander roots, you simply use the roots section of the coriander bunch and wash the dirt off.
You can purchase bunches of coriander with the roots still attached from most major supermarkets. If your supermarket doesn’t sell the bunches with the roots, then the stems are the next best thing to use.
The roots freeze well, if you wanted to keep a stash of them in the freezer for whenever you feel like Malaysian Chicken Satay from ‘A Little Taste of Asia’.