Preheat your oven to 200°C/Fan 180°C/Gas 6. Tip the quinoa into a sieve and rinse under cold water for a few mins. Tip into a pan. Pour in 150ml boiling water. Cover and bring to the boil. Turn the heat right down and simmer for 12-15 mins till the water has been absorbed and the quinoa is tender. Take off the heat.
While the quinoa cooks, trim the base off the broccoli, and cut into small florets. Thinly slice the stalk into rounds. Pull any ragged leaves off the Brussels sprouts. Scatter the sliced broccoli and the whole sprouts into a large roasting tin. Pour over 1 tbsp sweet chilli sauce, 1 tbsp tamari and 1 tbsp oil and toss everything well to evenly coat. Slide into the oven and roast for 15 mins.
Peel and grate the garlic clove and ginger and slide into a bowl. Grate in the lemon zest and squeeze in the juice from 1 half. Stir in 1 tbsp tamari and 1 tbsp olive oil till well combined.
Slice the cherry tomatoes in half. Drain the quinoa if necessary and tip into a bowl. Fold in the roasted greens and halved cherry tomatoes. Pour over the dressing and serve.