Toast nuts over low heat in a small skillet until crisp and fragrant. Place romaine in salad bowl and scatter the red onions down over the greens. In a small bowl, combine the marmalade, red pepper flakes, balsamic vinegar and fresh or dried rosemary using a fork or small whisk. Drizzle extra-virgin olive oil into the dressing until combined. Season the dressing with salt, to taste. Dress and toss salad and adjust seasoning.