Tortoises are creatures of habit and new foods have to sometimes be introduced slowly. Finely chop up some romaine, then finely chop up a very small amount of the new good stuff and mix it all up. Just keep doing this until your tortoise eats it all. Don't be afraid to let him get hungry. You are not starving him if there is a pile of food right in front of him.
Romaine alone is not a good diet and your tortoise cannot survive on that for very long.