Preheat the oven to 400° Line a large rimmed baking sheet with aluminum foil.
Place the diced sweetpotato in a large bowl with 2 teaspoons of the olive oil and toss to coat evenly. Sprinkle with salt and pepper. Arrange on the baking sheet and bake until tender, 18 to 20 minutes, stirring halfway through. When done, remove from the oven, transfer to a plate, and cool to room temperature.
Place the remaining 3 tablespoons olive oil, the zest, and the lemon juice in a bowl and whisk until well combined. Set aside.
While the sweetpotatoes are roasting, trim the cauliflower and cut in half. Shred on the large holes of a box grater. (The cauliflower will end up looking like grains of rice.) Transfer to a large bowl. Gently stir in the parsley, green onions, cranberries, mint, pepitas and sweetpotatoes. Re-whisk the dressing and drizzle over the tabbouleh. Stir to combine.
Season with salt and pepper to taste.