Preheat oven to 400° F. Toss squash cubes, olive oil, nutmeg, salt and pepper in a bowl and tip onto a baking sheet. Roast for 25–35 minutes, until squash is lightly caramelized. Remove from oven and set aside.
Place walnuts on a small baking sheet and toast in the same 400° F oven for 5–8 minutes, until slightly browned. Remove from oven, sprinkle with a pinch of salt and set aside.
In a large bowl, toss together arugula, spinach and radicchio. Add all of the lime zest and the juice from ½ of the lime to the greens. Season the greens with salt and pepper, and toss to combine lime zest, juice and seasonings.
Lightly dress the greens with the pomegranate vinaigrette and toss to coat greens.
Transfer the greens to a serving bowl or 4 individual plates.
Add the squash to the bowl used to toss the greens in and lightly dress with the pomegranate vinaigrette. Add the squash to the plated greens and garnish with toasted walnuts. Serves 4.