Peel sweet potatoes and parsnips; cut into sticks about 1/2 inch by 3 to 4 inches. Lightly coat a 12- by 17-inch rimmed baking pan with cooking oil spray. Place vegetables in pan, cover tightly with foil, and bake in a 400° regular or convection oven until just tender when pierced, 35 to 40 minutes.
Meanwhile, in a small bowl, combine maple syrup, brown sugar, bourbon, butter, orange peel and juice, and cardamom.
Increase oven temperature to 450°. Remove foil from pan and sprinkle pecans over vegetables. Pour the syrup mixture over vegetables and pecans; turn pieces with a spatula to coat evenly.
Bake until syrup mixture thickens and sticks to vegetables, 25 to 35 minutes longer, turning pieces often to prevent scorching. Transfer candied vegetables to a serving dish. Season to taste with salt.