With the rack in the middle position, preheat the oven to 220°C (450°F).
On a rimmed baking sheet, toss the vegetables with the vinegar and oil. Season with salt and pepper. Roast until the vegetables are tender, about 20 minutes, stirring a few times during cooking. Skin and dice the tomatoes.
In a saucepan over high heat, bring the broth, vegetables and lentils to a boil. Reduce the heat and simmer until the vegetables and lentils are very tender, about 5 minutes. Purée in a blender, adding broth as needed. Adjust the seasoning.
Serve the soup as a main course with your favourite cheese and store-bought naan bread.