Preheat the oven to 400°F then line two baking sheets with parchment paper.
Arrange the tempeh, squash, onion and potatoes on top then spray or toss with high heat oil. If using brussels instead of kale add them at this point as well. Bake in the oven for 10 minutes. Remove baking sheets from oven and set aside.
Meanwhile, whisk together the marinade in a measuring cup or small bowl. Using tongs, transfer the tempeh pieces to a large bowl then pour the marinade over top. Toss until evenly coated and allow to sit for at least 5 minutes.
Transfer marinated tempeh back to the baking sheets, add the kale (if using), then return the sheets to the oven for 15 minutes.
Prepare the tahini dressing as they continue to bake by whisking everything together in a measuring cup or small bowl. Add water as needed to thin. The amount will vary based on how thick your tahini is. I needed about 3 tablespoons.
Once the vegetables are golden and tender, remove from the oven. Serve veggies and tempeh warm, drizzle with tahini dressing and enjoy!