Heat your oven to 200°C/Fan 180°C/Gas 6.
Cut the butternut squash in half lengthways. Scoop out and discard the seeds. Cut the squash into 2 cm cubes. You can leave the skin on as it will soften as it cooks.
Remove any scruffy outer leaves from the sprouts, but keep them whole. Peel and thickly slice the onion.
Tumble the squash, sprouts and onion onto a baking tray. Drizzle over 2 tsp oil. Season. Toss together. Slide into the oven and roast for 30 mins. Turn the veg over after 15 mins.
Zest and juice the orange. Set the zest aside for later. Peel and grate the garlic cloves. Whisk the orange juice with the garlic and 2 tbsp tamari in a large bowl. Place the steaks in the marinade and set aside for 15 mins.
When the veg has cooked for 25 mins, heat a frying pan over a medium heat. Place the steaks in the pan, leaving the marinade in the bowl. Cook the steaks for 2 mins on each side for rare, 3-4 mins on each side for medium and 5 mins on each side for well done.
Set the steaks on a plate and cover with foil to rest and keep warm. Remove the veg from the oven and pour over the reserved marinade. Return to the oven to cook for a further 5 mins.
Arrange the rocket on two plates. Scatter over the roast veg, pouring over any juices and marinade. Top with the steak and scatter with the reserved orange zest.