Heat oven to 425 degrees. On two baking sheets,
arrange carrots, onion, and squash; drizzle
with 2 tablespoons oil, and season with salt and
pepper. Roast, turning once, until caramelized
and tender, about 30 minutes.
place lentils and shallot in a medium saucepan
and cover with water by two inches.
Bring to a boil, then simmer, covered, until
lentils are tender, about 20 minutes. Drain;
discard shallot. Season with salt and pepper.
Combine vinegar and mustard. Pour remaining
3 tablespoons oil in a slow steady stream,
whisking constantly. Toss lentils and celery
with vinaigrette and season with salt
and pepper. Spoon over roasted vegetables.
Garnish with celery leaves.