Preheat to oven to 425 degrees(F).
Make the BBQ sauce first. Heat the vegan butter on medium high in a medium sized sauce pan.
Once the vegan butter has melted, add the sweet onion. Sauté, reducing heat as needed until the onions are translucent, about 1-2 minutes.
Add the tomato paste and water to the sauce pan and whisk to combine.
Then add the brown sugar, maple syrup, apple cider vinegar, liquid aminos, Dijon, celery salt, garlic powder, pepper and salt. Whisk to combine everything.
Bring the sauce to a simmer, reduce heat to medium low, so it is just at a soft bubble. Simmer, whisking frequently for about 5 minutes. It will thicken slightly. Remove from the heat.
Cut your tofu into cubes and put them in a large mixing bowl, then pour about 1/4 of the sauce on top of the tofu. Toss to coat everything. Put the tofu on one side of a large sheet pan that is lined with parchment paper or a silicone mat. Spread it out evenly.
Then add the sweet potatoes to the same mixing bowl, pour another 1/4 of the sauce on top. Toss to coat. Put the sweet potatoes on the other side of the sheet pan leaving room for more veggies to go in the center later.
Sprinkle the tofu and sweet potatoes with a bit more salt and pepper. Roast in the oven for 20 minutes.
While the tofu and sweet potatoes are in the oven, add your broccoli and cauliflower to the same mixing bowl and pour another 1/4 of the sauce on top. Toss to coat.
Once the tofu and sweet potatoes have roasted for 20 minutes, remove them from the oven and add the broccoli and cauliflower to the center of the sheet pan.
Roast for another 20 minutes. Remove from the oven, toss everything and pour the remaining BBQ sauce on top.
Roast for 5 more minutes. Then taste and add a bit more salt and pepper if needed. Serve! This is also perfect for meal prepping. It reheats well!