Preheat oven to 425 degrees F (220 degrees C). Place potatoes in a medium saucepan. Add cold water, cover and bring to a boil. Reduce heat and simmer until barely fork tender, about 3 minutes. Potatoes should still be quite hard, or they will go mushy when you roast them.
Meanwhile, in a small bowl whisk margarine with lemon juice. As soon as potatoes are cooked, drain very well. Turn potatoes into a baking dish just large enough to hold them. Toss with lemon juice mixture. Bake in preheated oven, stirring occasionally until golden and cooked through, about 20 minutes.
Sprinkle with lemon peel, herbs or green onions. Add salt and pepper if using.