Preheat your oven to 425°F (220°C).
Remove the leaves and stem from the cauliflower and cut it into bite-sized florets.
In a mixing bowl, combine olive oil, cumin, coriander, paprika, turmeric, cayenne pepper (if using), salt, and pepper. Add the cauliflower florets and toss to coat evenly with the spice mixture.
Spread the seasoned cauliflower on a baking sheet in a single layer. Roast in the preheated oven for 25 minutes or until golden brown and tender, flipping halfway through.
While the cauliflower is roasting, prepare the quinoa or couscous according to package instructions.
In a small bowl, whisk together tahini, lemon juice, garlic, salt, and enough water to achieve your desired dressing consistency.
Once the cauliflower is done, assemble the bowls by placing a serving of quinoa or couscous at the bottom. Top with roasted cauliflower, cherry tomatoes, cucumber, red onion, and parsley.
Drizzle the tahini dressing over the bowls and serve immediately.