Heat grill to high. Put the sausages in a large roasting tin and grill for 8-10 mins until browning, then switch the oven on to 200C/180C fan/gas 6. Remove the tin from the oven and add the vegetables and garlic, then drizzle over the oil and toss in the paprika and some seasoning.
Roast for 30-35 mins more until the sausages and veg are mostly tender, then stir through the lentils and vinegar. Return to the oven for 5 mins until everything is heated through. Squeeze the garlic cloves out of their skins and stir the garlic into the lentils, then season to taste, stir through the parsley and serve.