Heat the oven to 200C/390F/gas mark 6. Toss the cauliflower with half the oil, a quarter-teaspoon of salt and some black pepper. Spread on an oven tray and roast for 20 to 25 minutes, stirring once or twice, until nicely browned. Set aside to cool.
In a bowl whisk the remaining oil with the vinegar, mustard, honey and a quarter-teaspoon of salt. Add the raisins and leave to soak for at least 10 minutes. Just before serving, transfer the cauliflower to a bowl with all the other ingredients. Pour over the dressing, toss gently, adjust the seasoning to taste and serve.