Preheat the oven to 425.
While the oven is preheating, coat the potatoes and radishes in 1 Tbsp. oil, spices and a sprinkle of salt. Mix thoroughly and place on a greased baking sheet or dish. Roast in the oven for about 15-20 minutes until the veggies are tender and crisp, mixing about half way through.
In the meantime, place the remaining oil in a pan and saute the garlic and half of the spring onions on medium-low for around 5 minutes.
When the potatoes & radishes are done cooking, add them to the pan and continue cooking for 1-2 minutes.
Assemble the tacos by adding a scoop of veggies and a scoop of beans to your tortilla. Top with lettuce, some of the remaining chopped spring onions, and whatever other topping you enjoy!