Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius). Line a baking sheet with parchment paper.

Place all vegetables on prepared sheet. Drizzle with oil and sprinkle with salt and pepper. Roast for 50–60 minutes, until the vegetables are starting to get some color.

Once vegetables come out of the oven, transfer them to a large soup pot. Add remaining ingredients, then turn heat to high and bring soup to a boil.

Once boiling, reduce to a simmer. Cook for two to three hours, until lentils are soft and falling apart. Taste and, if desired, add more salt and pepper to taste.