On the CCA side of things, role play consists of developing your character from a low level recruit, who is still very much human in their actions, emotions, and feelings, into a cold, calculated unit that follows orders to the letter and doesn't fail their superiors. Why don't they fail? Because failure as an experienced, high ranking unit (especially a commissioned Officer) results in death most of the time. As a recruit, you are human and will make mistakes. You will also be nervous in dealing with situations you're not familiar with, such as handling a weapon, or detaining a citizen for the first time. As you move up in rank and gain experience, this sort of feeling gradually fades away. When it comes to amputating citizens, ranks below 01 normally have a tough time doing so, as they have regrets and feel remorse. Over time, you become more desensitized to death, but your character should never lose their emotions fully. Even Officers have their regrets.
When it comes to dealing with your subordinate units when you're in a position of power, you should be firm and strict, but not unnecessarily harsh. Commanding units requires experience and appropriate rank. It also requires your character to be respected for their accomplishments. Respect must be earned, it's never given. It's important to be respectful to your subordinates, unless they give you a reason not to be, such as blatantly disrespecting you, or disobeying orders, in which case, you should take disciplinary action against them.
You must remember that you're on the same team as your superiors and your subordinates at all times, and you should never allow any position of power you hold to get to your head or get the best of you. Do your duty, but don't over-do your duty. Don't strive to be feared, strive to be looked up to and respected. Get your hands dirty with your subordinates, and they will look to you for guidance and follow your orders with pride.