When speaking to high-ranking people, mainly the emperor and shogun, you don't just say "Hey Ashikaga, listen", no, that is disrespectful and might get you into trouble, you can make enemies that way too.

Here are some ways of how to speak with the Shogun:

Kubo-Sama: "Kubo" is another word for Shogun, this was the most common way of addressing the Shogun.

Ue-Sama: "Above", also used to address the Shogun in the Sengoku Jidai.

Shogun-Sama: Good enough, but not as good as the ones listed above.

"Shogun Ashikaga" is wrong, but you may use it if you wish.

Remember, the Shogun is the boss in this game, he is the head of the government, the representitive of the emperor, you have to be respectful when speaking to him or else you will make enemies, face punishment, or possibly be declared a rebel by the government.

For the emperor, the ones used above aren't recommended, rather the titles used by knights to address their masters: "Your Highness/Excellency/Exaltedness", and other fancy ways of addressing those who hold high titles.

If any of you have any questions, please post them here.

Should Romaji really be used in this roleplay? And I don't suppose we can call a general senior to our own a "senpai".

I guess if he is slightly older than you, and something of a Mentor, you could.