You can definitely make this using fresh vegetables. Anything goes, such as zucchini, peas, green beans, sweet potatoes, carrots, mushrooms, eggplant, and so on. When using fresh vegetables, bear in mind dense ones (pumpkin or carrots for example) take longer to cook than soft ones (like mushrooms or zucchini), so you'll need to bake the dense ones for a while before adding the softer ones, so everything is done at the same time.