Preheat your oven to 425°F (220°C).
Remove the leaves from the cauliflower and chop it into bite-sized florets.
In a mixing bowl, combine the olive oil, cumin, coriander, paprika, turmeric, cayenne pepper, salt, and pepper. Add the cauliflower florets and toss well to coat evenly.
Spread the seasoned cauliflower evenly on a baking sheet and roast for 20-25 minutes, until golden brown and tender, tossing halfway through.
While the cauliflower is roasting, prepare the grains according to package instructions. Set aside.
In a small bowl, whisk together tahini, lemon juice, and a few tablespoons of water until smooth. Adjust the consistency by adding more water as needed, and season with salt to taste.
Once the cauliflower is roasted, assemble the bowls: Divide the cooked quinoa or brown rice into four bowls. Top each with roasted cauliflower, cherry tomatoes, cucumber, red cabbage, parsley, and red onion.
Drizzle the tahini sauce over each bowl before serving.