Place the potatoes, peppers, fennel, zucchini, and garlic in a large baking dish. Drizzle the olive oil evenly over the vegetables. Sprinkle the salt, bouillon powder, and rosemary over the top. Stir the mixture until the vegetables are coated.
Bake in the preheated oven until tender, stirring occasionally, about 1 hour. Stir the balsamic vinegar into the vegetables; serve immediately.