1. Clearly articulate the rules for converting from Arabic numerals to Roman numerals. (The steps your own brain takes in doing a conversion, even if you aren't necessarily consciously aware of the process.)
2. Convert these rules to C++ code. (Without using functions or arrays.)
So, go devote some time to #1, above. Ideally, breaking the process up into multiple small steps, each clearly and unambiguously defined.
Then attempt #2, above.
If you still have difficulty, post #2 above - between code brackets, and reasonably formatted and commented - and we'll see what we can do. Okay?