Heat oven to 400˚F. Cut the fingerling potatoes into ¼” thick slices. Toss with olive oil and spread into a single layer on a sheet tray covered with parchment paper. Roast until tender and browning, 30 minutes.
While the potatoes are roasting, combine ingredients for chimichurri sauce in a small bowl. Whisk together until well combined.
Once potatoes are done, combine with pinto beans and ¼ cup or so of the chimichurri. Stir until the beans and potatoes are well coated with the sauce.
Heat the tortillas and assemble the tacos with a layer of spinach, a few spoonfuls of the bean mixture, a tablespoon of crumble cheese, and extra chimichurri as desired.