Make the sweet potatoes + black beans: Preheat oven to 425. On a rimmed baking sheet, toss diced potatoes and beans with oil, sprinkle on spices and roast for 15-20 minutes, until potatoes are tender.
Make Enchilada Sauce: Heat oil in small saucepan over medium heat. Whisk in arrowroot powder and cook for about 30 seconds. Add spices, garlic and tomato paste and whisk continuously as it forms a paste, about 30 more seconds. Gradually incorporated stock, whisking well after each addition. To avoid lumps, continue whisking until smooth. Reduce heat to a low simmer and cook until sauce thickens, about 5 minutes. Sauce will stay good in a glass jar, tightly sealed in the fridge for 3 weeks.
Make Enchilada Bowls: Place greens in the bottom of bowl followed by other options and top with enchilada sauce.