Nonstick vegetable oil spray
1 pound red-skinned potatoes, unpeeled, scrubbed, cut into 1-inch pieces
1 pound celery root (celeriac), peeled, cut into 1-inch pieces
1 pound Hakurei turnips, peeled, cut into 1-inch pieces
1 pound carrots, peeled, cut into 1-inch pieces
1 pound parsnips, peeled, cut into 1-inch pieces
1 pound beets, peeled, cut into 1-inch pieces
2 onions, cut into 1-inch pieces
2 leeks (white and pale green parts only), cut into 1-inch-thick rounds
2 tablespoons chopped fresh rosemary
1/2 cup olive oil
10 garlic cloves, peeled
Position 1 rack in bottom third of oven and 1 rack in center of oven and preheat to 400°F. Spray 2 heavy large baking sheets with nonstick spray. Combine all remaining ingredients except garlic in very large bowl; toss to coat. Season generously with salt and pepper. Divide vegetable mixture between prepared sheets. Place 1 sheet on each oven rack. Roast 30 minutes, stirring occasionally. Reverse positions of baking sheets. Add 5 garlic cloves to each baking sheet.
Continue to roast until all vegetables are tender and brown in spots, stirring and turning vegetables occasionally, about 45 minutes longer. (Can be prepared 4 hours ahead. Let stand on baking sheets at room temperature. Rewarm in 450°F oven until heated through, about 15 minutes.)
Transfer roasted vegetables to large bowl and then serve.
Tested and Approved by Boston Organics (Chris McIntosh)