Preheat oven to 425 degrees.
Line a sheet pan with parchment paper and arrange the sliced potatoes in one layer, with some of the potatoes overlapping. Drizzle with olive oil and season with salt and pepper.
Roast in the oven for 30 minutes or until the potatoes are fork-tender and the edges are slightly crisp and browned.
Evenly sprinkle half of the shredded cheese on top of the cooked and browned potatoes and arrange the shredded corned beef on top of the cheese and top with the remaining shredded cheese. Bake for an additional 5-8 minutes or until the cheese is melted.
Remove from oven and top with sliced green onions and a couple of dollops of sour cream.