Cook risoni in a large saucepan of boiling salted water until al dente (4-5 minutes). Drain and rinse under cold running water. Transfer to a bowl, drizzle with oil and mix to combine.
Meanwhile, combine lemon juice, onion and garlic in a small bowl and stand until onion turns pink (2-3 minutes). Add to risoni with preserved lemon, herbs and spinach, season generously to taste and toss to combine. Serve immediately with roast chicken and natural yoghurt.