Romano cheese is a hard and sharp flavoured cheese that is usually served grated on top of foods. Sharp cheeses get their sharp flavour from sitting in an acidic environment, such as a brine, for a long period of time. Romano cheese is one of the oldest cheeses in the world, possibly produced as early as the time when Jesus Christ lived, according to the Cheeseforum.org.
You can use Parmesan cheese as a substitute for Romano because it is aged for the same amount of time, making it a hard cheese that crumbles and can be grated easily. Both cheeses also have similar textures, although Parmesan is made from cow's milk, so there may be a difference in flavour. Fine Parmesan can be found in speciality stores. Cheaper alternatives can be found in most grocery stores.
Aged Gouda is another substitute that you can use for Romano cheese. Gouda is a cheese primarily made in the Netherlands. More aged types of Gouda are called "oud." The older the Gouda, or the longer the Gouda is aged, the more granular the cheese will be. Aged Gouda has a similar flavour and texture as Romano.
If you are vegan, or cooking for someone who does not eat any animal products such as milk and cheese, oil-cured olives can be used as a nondairy alternative to Romano cheese. These can be found canned in grocery stores. You can chop them up and use them as you would Romano cheese.