@bigusdickus
Not all roleplay includes sex. In fact, I'd venture to say that most roleplaying does not include sex.
Best way to increase your erotic writing skills is to read romance novels and free online erotica.
Maybe download Replica or AI Dungeon on your phone to practice on.
Good luck in finding a RP partner / teacher.
A rather generous girl taught me in my teenage years .... my best advice that she gave me, ask yourself "what would I do in this situation?", and then write it down. If you don't like the results, then read more books / watch movies with main characters who act like what you want to be ... and learn from them. Practice by writing a backstory for your character, and fleshing out your character design.