Preheat oven to 425F. Press tofu for 15 minutes either using a tofu press or by wrapping it in a dish towel and placing a heavy object (such as a cast iron pan) on top.
While the tofu is pressing, add the chopped cauliflower and sweet potato to a large bowl. Drizzle with oil and seasonings. Toss to combine until evenly coated.
Once tofu is done being pressed, cut it in half lengthwise. Then, cut into small cubes (I do about 6 cuts in one direction and 4 cuts in another).
In another large bowl, add the oil and harissa and whisk to combine. Add the tofu and gently toss with your hands to coat. Add the arrowroot and toss again.
Add the tofu, cauliflower and sweet potato mixture to a baking sheet. If you want maximum crispiness, feel free to spread the mixture out amongst two pans so nothing is overlapping. But if you want less dishes (me!), then one baking sheet will work just fine. Bake for about 18 minutes, then turn to broil for a few minutes at the end to help it get a nice color.
In a small bowl or jar, add all of the harissa tahini sauce ingredients and stir or shake until combined.
Assemble your bowl starting with arugula, then the roasted tofu, cauliflower and sweet potato, and topping it all off with a drizzle of harissa tahini sauce. Enjoy!