Just like to drop my opinion! What everyone has said so far is true, however, RP is more then simply writing a scenario, you can think of RP as multiple people coming together to chip in ideas and pieces to create a beautiful adventure where everyone can shine. In most threads everyone is an equal capable of anything (within reason). That is what makes it exciting, liberating and fantastic.
The only person that is above the RPers however is a GM, and it is very misleading to say that they control the story in my opinion, players are unpredictable and will almost never do what you expect them to do. So for me personally, a GM should create an environment that has a problem, whether it be a villain or getting something, give the players a reason to accomplish said thing, then let go of the reigns and to respond to the players. This is a key point. Having the players respond, then having the GM react, then respond, then the players will respond, rinse and repeat.
This does not mean that rules cannot be established. But rules that restrict the players severely will make it very unappealing, like filling roles, (IE we need a navigator, tank, and dps), restricting types pf characters (We cannot have people that see the future) and finally player minimums are somewhat daunting, but not the worst.
Another thing I would like to add. Jumping into plots are fine, unless it is a continuation thread and you had to be there in the previous thread or it's been a little while you should ask. But do not take control away from GMs or Players. Wanting to contribute to PK's death is completely fine. However, appointing yourself was a wrong move. But we can all make amends.
One final point, you generally get better with experience, if you want to get better at Phansite RP, try lurking in RP threads and sussing out things that people do that you can incorporate. Or you can try to play an established persona character so you do not accidentally GodMode with an out of proportion character. Generally Persona Characters have defined personalities through the game and neat personas so I recommend one to start off, just an opinion though!
Wow I really went off on a tangent, my bad! Anyhow! Let's finish on a positive note! Your writing is fantastic for a beginner here! You just need to learn that you are RPing and not writing. To reinstate points already said, you assume the role of one character, that character alone cannot dictate the story, but working together with other characters can change the story and hopefully with the GM create a brilliant thread! I hope to see the new and improved Rosie soon! If you ever need advice or anything my discord door is open! rexofired#6602 Feel free to add me and ask questions!