sweet potatoes, peeled and cut into 1-in. pieces
sweet onion, cut into 1-in. pieces
carrots, peeled and cut into 1-in. pieces
extra-virgin olive oil
smoked kielbasa or polish sausage, halved and cut into 1-in. pieces
yellow squash, cut into 1-in. pieces
zucchini, cut into 1-in pieces
salt
Dijon mustard for topping