Place poblano peppers on a broiler pan on the highest shelf in the oven, 1 inch below the broiler element. Heat the broiler's oven to high. Broil until fifty percent of the tops are charred, about 5 minutes. Flip and repeat on the other side, about 5 minutes more.
Place peppers in a large plastic bag. Allow peppers to steam as they cool, about 15 minutes.
Meanwhile, bring a large pot of salted water to a boil. Add pasta and cook, stirring occasionally, until tender, 4 to 5 minutes. Drain.
Peel the loosened skin from each pepper. Wipe with a paper towel to remove any remaining pieces. Avoid running peppers under water; this will diminish the charred flavor.
Place peeled peppers, canned peppers, romaine, onion, cilantro, and garlic in a blender. Blend until well combined.
Heat oil in a large skillet over medium heat. Pour in pepper mixture and saute until tender, 3 to 5 minutes. Mix cream cheese and sour cream together and add to the skillet. Stir in lemon juice. Simmer sauce for 10 minutes. Add pasta to the skillet and mix well.
