Bring 4 1/2 cups water to boil in large saucepan. Add couscous and currants. Cover, remove from heat and let stand 5 minutes. Fluff with fork. Transfer to large bowl and cool. Mix all remaining salad ingredients into cooled couscous. Pour dressing over salad and toss. Season with salt and pepper. (Can be made 1 day ahead. Cover and chill.) Line large bowl with romaine. Add salad.