Preheat oven to 425° F. In a large bowl whisk together extra virgin olive oil, balsamic vinegar, ginger and kosher salt; whisk until salt is dissolved. Add squash, fennel, sweet potatoes and red onions; toss to coat and transfer to a large rimmed baking sheet. Roast 45 to 50 minutes, flipping vegetables once about halfway through. Remove from oven and let cool to room temperature.
While vegetables are roasting, make dressing. In a small bowl, whisk together tamari (or soy sauce), water, garlic and sugar until sugar is dissolved.
To serve, transfer roasted vegetables to serving bowl or platter and top with dressing. Serve at room temperature.