Bake peppers on a lightly greased aluminum foil-lined baking sheet at 400° for 30 minutes or until peppers look blistered.
Place peppers in a zip-top plastic bag, and seal. Let stand 10 minutes to loosen skins. Peel peppers; remove and discard seeds. Cut peppers into thin slices. Set aside.
Sauté garlic in hot olive oil in a large skillet over medium heat 2 minutes. Add spinach, 1 bag at a time, and sauté just until spinach begins to wilt. Add salt and pepper. Cover and reduce heat to medium low. Cook 2 to 3 more minutes or until spinach is completely wilted.
Drain spinach and return to skillet. Stir in sliced roasted peppers, pine nuts, and, if desired, vinegar. Cook over medium heat 5 minutes or until thoroughly heated, gently tossing to coat.
Kitchen Express: Substitute 1 (7-ounce) jar roasted red bell peppers, drained and sliced, for 2 red bell peppers. Omit baking procedure, and proceed as directed.