There are endless possibilities for what to add to risotto. Once you understand the cooking process, you can be creative with your own variations. When adding vegetables to risotto, deciding when to add them depends on the vegetable itself. Risotto takes about 15 minutes to cook once you start adding the liquids. Vegetables such as carrots or mushrooms that can withstand 15 minutes of cooking without getting mushy can be added at the beginning of the process. Asparagus or zucchini will be overcooked, however, so it's best to sauté it separately and add it at the end of the cooking process.