If you go to the resources tabs on this forum there is a lot of info like this-
Suggested Ingredients
Best - These gutloading ingredients are best because they are highest in calcium, low in phosphorus, oxalates and goitrogens. They should be the primary components of your gutload: mustard greens, turnip greens, dandelion leaves, collard greens, escarole lettuce, papaya, watercress and alfalfa.
Good - These gutloading ingredients are good because they are moderately high in calcium and other vitamins/minerals. They should be used in addition to those from the previous category: sweet potato, carrots, oranges, mango, butternut squash, kale, apples, beet greens, blackberries, bok choy and green beans.
These fresh fruits and vegetables can be combined with dry gutload mixes or home made mixes for optimal well-rounded nutrition. Dry ingredients can include: bee pollen, organic non-salted sunflower seeds, spirulina, dried seaweed, flax seed and organic non-salted almonds.
Romaine will not kill your chameleon but should only be a small part of what you feed/gutload the insects with. I used it mostly because it provided moisture.