What that does is lead the game to reference the default texture of the model, which by and large in the Romans case is the julii texture, however the defaults of some of the standard bearers go to non-julii textures so it will look a bit odd.

dmb won't recognise romans as a faction.

However, it pretty much is just as easy as making the other roman factions reference the julii texture in dmb. You can change other stuff such as the unit cards and the banners as well if you like, but you might prefer to leave those as is.