Preheat your oven to 200°C/Fan 180°C/Gas 6. Trim the squash and slice it in half. Scoop out the seeds (see our tip below) and slice the squash into small chunks. Peel the red onion and cut it into thick wedges. Add the squash and onion to a large roasting tin and toss with 1 tbsp olive oil and a little salt and pepper. Slide into the oven and roast for 30-40 mins, turning halfway, till tender and slightly browned at the edges.
Meanwhile, drain and rinse the chickpeas and shake them dry. Tip them into a large bowl. Peel and grate in the garlic. Add 1 tsp Dijon mustard, 1 tbsp cider vinegar and 1 tbsp olive oil. Season with salt and pepper and stir to mix.
When the squash and onion have roasted, tip them into the bowl of chickpeas. Crumble in the feta and add the rocket. Fold the salad together and serve straight away.