Preheat the oven to 200 degrees.
In a large baking tray, combine the cauliflower, olive oil, chilli powder, garlic, crushed red pepper flakes, and a pinch each of salt and pepper. Toss well to evenly coat. Transfer to the oven and roast for 30 minutes, until tender and lightly charred.
Meanwhile, chop up your cucumber. Add to a bowl with the salad leaves.
Now make the vinaigrette. Combine all ingredients in a bowl and mix until completely smooth. Taste and adjust the salt and pepper.
Toss the roasted cauliflower in with the salad. Add a little of the vinaigrette and toss to combine. Top the salad with avocado and feta cheese. Serve and enjoy!