HEAT oven to 450ºF.
PLACE first 5 ingredients in 15x10x1-inch pan. Add 2 Tbsp. dressing; toss to coat. Spread to evenly cover bottom of pan.
BAKE 40 to 45 min. or until vegetables are tender and golden brown, stirring occasionally. Spoon into large bowl. Add spinach; toss lightly.
TOP with bacon, nuts and remaining dressing.