I go with what's on the game cover. And usually, that's Roman, so that is what is correct.
Roman: I, II, III, IV, V, etc.
Arabic: 1, 2, 3, 4, 5, etc.
I'm inconsistent :P
I'm a witless failed comedian who says "One, two, three, etc"
I go with what's on the game cover. And usually, that's Roman, so that is what is correct.