Even the Turkish Napoleon can lose a battle. However, the sheer size of the armies in the field probably mean that whoever wins, it will take heavy casualties.
I'm betting either in a Roman pyrrhic victory or a heavy Roman defeat, because that is Iskandar we are talking about, with a veteran army no less. Besides, the World War One is going to be a war for Roman Sucession, isn't? I'm also willing to bet that the Kaisar will not go away from the battlefield unscathed, and maybe Nineveh will be a factor for Roman weakness for the next few years.
A lot of veteran troops on Iskandar's side, but many of which have loot from past wars and are tired of war and ready to settle down. They may on the over cautious side. Iskander also has a lot of undisciplined troops who may make impulsive attacks, get repulsed then panic. The Romans seem to have a more cohesive force which should play to their strengths. I would not be surprised to see Iskandar dying trying to rally troops fleeing from the field.