Preheat your oven to 375 degrees Fahrenheit.
Toss the potatoes with 2 tablespoons of olive oil on a large sheet pan.
Season them generously with salt and pepper, then toss to coat evenly.
Roast the potatoes, stirring once halfway through the process until they attain a golden-brown hue and become tender, which usually takes approximately 30 minutes.
Set the roasted potatoes aside.
Complete the bean preparation: Heat 2 tablespoons of olive oil over medium heat in a spacious and deep skillet. Add the finely chopped garlic and sauté until it turns soft and aromatic. As soon as the edges of the garlic begin to take on color, pour in the red wine and simmer until the wine reduces by half, typically taking about 5 to 10 minutes.
Using a slotted spoon, carefully transfer the cooked beans (you should have approximately 7 cups) into the reduced wine mixture in the skillet. Add roughly 2 cups of the cooking liquid from the beans, ensuring it adequately covers most of the beans. Then, include the olives, prunes, and an additional ¼ cup of olive oil. Allow this mixture to simmer over medium heat, stirring periodically, until the flavors harmonize and the liquid slightly thickens to form a sauce, typically within 10 to 15 minutes. Season it to your taste with salt and pepper.