Roasted Winter Veggies With Lentils

1/2 pound carrots, halved lengthwise
1 red onion, cut into 1-inch wedges
1 delicata or carnival squash, halved, seeds removed, cut into 1/2-inch slices
5 tablespoons olive oil
coarse salt and freshly ground pepper to taste
1/2 cup French green lentils, rinsed
1 shallot, halved
4 teaspoons apple cider vinegar
1 teaspoon Dijon mustard
1 stalk celery, thinly sliced, leaves reserved

1. Heat oven to 425°F.  Arrange carrots, onion and squash on two rimmed baking sheets.  Drizzle with 2 tablespoons oil and season with salt and pepper.  Roast, turning once, until tender and caramelized, about 30 minutes.  
2. Place lentils and shallot in a medium saucepan and cover with 2 inches of water.  Bring to a boil then simmer, covered, until lentils are tender, about 20 minutes.  Drain an discard shallot;  Season with salt and pepper.
3. Combine vinegar and mustard in a small bowl and drizzle in 3 tablespoons oil in a slow steady stream, whisking constantly.  Toss lentils and celery with vinaigrette; season with salt & pepper.  Spoon over roasted veggies and serve garnished with celery leaves.