Preheat the oven to 450 degrees F (230 degrees C). Lightly oil a large baking dish.

Stir together potatoes, water, olive oil, lemon juice, garlic, salt, and pepper in a large bowl until potatoes are evenly coated. Pour into the prepared baking dish.

Roast in the preheated oven until potatoes begin to brown, about 40 minutes. Season potatoes with oregano and mint. If mixture appears dry, pour another 1/2 cup water into the dish. Return to the oven and bake until potatoes are very tender, about 40 minutes more. Top with feta cheese to serve.