need help with modding a unit...and frozen peas.

[Ciaran]

First of all, did you use the -show_err command line? If not, do so, perhaps it´ll give you a hint where you went wrong.
Then, you don´t need to give the ownership to Greece and Germans just because you used their models, ownership defines which faction may use a unit in the game. There could be the reason of the crash, because if you change ownership, you must make sure the unit has a texture defined for every faction which may use it. And perhaps you misspelled the Julii faction in ownership, I think it has to be romans_julii ( with the _ instead of a space).
[edited in regard of Bwian´s post] It is also possible that it´s a space instead of the _ I´m not sure there right now, but definitely it´s one or the other, not both. Look at how it´s done with the unmodded Roman units, if CA did it, it´s usually right (in terms of working).
I hope that was helpful in a way.