Preheat the oven to 200°C, 180°C fan, gas 6. Cut the fennel vertically into eight wedges, keeping the core attached to each wedge. Slice the aubergine into 1cm rounds and arrange in a large roasting tin with the fennel and sausages.
Snip the tomato vine into three. Place two of the vines on to the roasting tin, saving the remainder to make a spicy tomato and harissa dressing.
To make the dressing, finely chop the reserved tomatoes and place in a bowl with the oil, garlic, harissa paste and lemon juice.
Pour this mixture over the vegetables and sausages, making sure everything is lightly coated.
Roast in the oven for 35-40 minutes until golden and cooked through.