Hello,

So, concerning that suggestion, I will forward it, but it's unlikely to be implemented.
Kenjutsu (sword arts) are different than bukijutsu (weapon arts).

I am unfortunately unable to provide info on Roshi's and Yagura's appearence in events as it stands now, they may or may not appear.

Jinchuriki treasure is unlocked at lvl 65

No ninja has a fixed rate to be drawn in a treasure, and all rare ninjas have the same chance of being drawn. (You have the same chance to draw Bee Samehada and Yagura).