Preheat the oven to 400F and line a cookie sheet with parchment paper.Dice potatoes so that they're all about ½" in size. Spread evenly in a single layer on parchment paper. Drizzle with 1 Tbsp olive oil.Roast in the oven for 30 minutes, turning half way through.Meanwhile, dice onion and pepper to the same size as the potatoes.When the timer goes off, toss the onions and pepper with the potatoes. Drizzle the remaining 1 Tbsp olive oil over the vegetables. Season liberally with salt and pepper and roast for another 20 minutes.Potatoes are done when they are mostly golden brown in color.