we know they could write.

we just don't have anything that they wrote, that survived.

at least, we don't think we do; we've been able to trace technical roman documents about seafaring and agriculture to pre-roman carthaginian sources. they exist, to us, simply in latin. but, we can decode them, and figure out where they came from.

there may be things that we only know from latin that are ultimately translated german or celtic works, we just haven't figured it out yet.