Preheat the oven to 450 degrees. Break the cauliflower into small florets. Toss the cauliflower with garlic, pepper flakes, fennel, coriander, turmeric and olive oil on a rimmed baking sheet. Season with a good bit of salt and pepper.  After 15 minutes, toss the cauliflower to promote even browning. Continue to cook for another 15-20 minutes, until you have some nicely charred bits. Remove from oven, transfer to a large platter and top with herbs and feta. Can be roasted a few hours ahead and served at room temperature as well.