How do you initiate sexual roleplays?

Sooo I recently just talked to my fiance and asked if he would like to roleplay with me. I wanted to try doing the rape roleplay, and he agreed to it. Of course, this is all consent from him and me.

But idk, how do people start role playing with their partners? Do you guys have any suggestions with how to start it or maybe some small planning ideas to get the role playing to be a good one?