Preheat oven to 425°F. Line a baking sheet or large roasting pan with parchment paper.
Toss cauliflower florets with 2-3 tablespoons of canola oil, about ¼ teaspoon salt, and a few strong turns on a pepper mill. Spread out the cauliflower on the parchment paper on the baking sheet. Roast for about 30 minutes, or until the cauliflower florets are have started to crisp and turn golden brown at edges and places where they're touching the parchment. Remove pan from oven and scrape the cauliflower into a bowl so you can re-use the pan.
Decrease the oven temperature to 325°F. Line baking sheet with new parchment paper.
If your walnuts aren't already toasted, spread them out the parchment paper and toast for about 10 minutes, or until they start to darken and you can smell nuttiness in the air. Remove from oven, scrape the toasted nuts into a bowl. You can put them in the same bowl with the cauliflower.
Spread the chickpeas out on the same parchment paper. Roast in oven for about 15 minutes or until the chickpeas start to darken and look slightly dry. Remove from oven and pour into bowl.
Add fresh parsley leaves to bowl with roasted cauliflower, toasted walnuts, and roasted chickpeas. Drizzle olive oil and sherry or pomegranate vinegar. Toss to coat. Season with salt and pepper to taste.
Add celery, pomegranate, avocado, tofu or tuna at the very end, toss gently (especially with avocado). Adjust salt and pepper accordingly.
Serve at room temperature.