Well, there's a small question of numbers. "Chief of Indians" is unlikely to control more than 1000 or so population, so several hundreds to couple of thousands legionnaries are likely to double local population and actually control the chief. And why do you think that legionnaries didn't know squat about how to farm or do crafts?
Probably means he doesn't know much about the Roman army. I'm not exceptionally knowledgeable in that area, and even I know that they weren't nearly that specialised, and were required to know how to set up what amounts to a small town, among other things.
Better late than never:
What I meant was, that the Roman soldiers could have hardly survived as farmers without the basic necessary things - European crops, European animals etc. If they were introduced into a
completely unfamiliar enviroment with less than a bare minimum to survive, they'd have to either deal with the natives, or take the food from them by force.
Which leads me to the second point: I don't think that more than a hundred of them would survive the journey. Most ships would sink, the rest would scatter and the remaining survivors would be in a very bad shape. Certainly bad enough to prevent them from conquering anybody right upon landfall.
Cooperation with the natives would be
absolutely essential for their survival. In the end, they'd assimilate into the local population and enrich it with some parts of their culture and technology (shipbuilding, construction, alphabet etc.).