Preheat the oven to 400°F (200°C). Toss the cauliflower florets in the olive oil then add to a large oven-safe pan or roasting tin. Season with salt and pepper and roast for 20 minutes, until the cauliflower starts to soften.
Remove the pan from the oven and turn over the florets. Add the edamame, cherry tomatoes, garlic, oregano, chili flakes (if using), and vegetable stock. Cover with foil and return the pan to the oven for 30 more minutes.
Remove the pan from the oven and squish the tomatoes gently with a fork to release the juices. Crumble over the feta cheese and bake, uncovered, for another 10 minutes.
Remove from the oven and scatter fresh basil leaves over the top and serve.