Round zucchini are simply just a variety of the zucchini squash. It's an heirloom varietal that grows more in bush form than a long trailing vine. The zucchini mature in about 45 days and result in a 3-4″ maximum (some are smaller) round shape. You could roast, fry them or mash them as you would potatoes. They are also a great addition to salads and pastas.