Preheat the oven to 375 degrees.
In a large roasting pan (or two smaller pans), layer the potatoes, eggplant, zucchini, onions, garlic, tomatoes, and parsley.
Pour in the olive oil.
Season generously with salt and add freshly ground black pepper.
Add in the water.
Mix everything until well combined.
Roast in the oven for 1 ½ - 2 hours, stirring the vegetables every 20-30 minutes.
You'll know it's done because the potatoes will be tender and the vegetables' edges have slightly crisped.