sure you can add a veggie to your risotto. With spinach, I would just stir the raw stuff into the cooked risotto before you add the last butter and cheese.
With the others, I would saute them and then stir them into the risotto towards the end of cooking time, so their flavor gets incorporated.
It must be cooler where you are than here in New York. No way could I possibly think of cooking risotto in this 100-degree heat!