Heat the oven to 400°. Place the potatoes on a baking sheet with 1 tablespoon of the olive oil and the salt and pepper and toss to coat. Spread the potatoes out on the pan so that they cook evenly, and roast for 20 minutes. Add the poblanos and roast until the potatoes are tender and browned, about 20 minutes more.
While the potatoes roast, pulse the jalapeño and garlic in a food processor. Add the remaining olive oil, the cilantro, and the vinegar with a pinch of salt and pepper and pulse to combine. Taste and add vinegar, olive oil, salt, or pepper, if needed.
Transfer the hot potatoes to a shallow bowl and toss with the salsa. Serve warm or at room temperature.