Prepare a baking sheet with foil and cooking spray. On half of the sheet, add diced parsnips, 2 tsp. olive oil, and ¼ tsp. salt. On the second half of baking sheet, add sweet potatoes, 1 tsp. olive oil, and a pinch of salt and pepper. Toss each half separately to evenly coat and spread into a single layer. Place in oven and bake 15-18 minutes until sweet potatoes and parsnips are tender. Remove from oven and cool for 5 minutes. Sprinkle seasoning mix on sweet potatoes and parsnips. Measure out 2 cups of sweet potatoes to use for burgers. Toss the remaining parsnips and sweet potatoes together and set aside.