Well the person above stated that you probably drew about 300 scrolls so 600-700 scrolls to either get sasuke or ay.

You can get han and roshi at 200-220 at their respective treasures.

Personally, I don't think ay is that great especially if you are f2p-casual spender. He might get better because of the new cloud ninjas arriving such as samui and skillbooks(but this would mean you have to invest in him more)

Roshi is a great ninja especially if he managed to scale his stats and survived till later rounds. Han remove shields and buffs so he's great against blitz. These two ninjas might not be compatible with your current barrier ninjas(onoki, danzo, darui) so think about that.

Depends on what you need. What are your current lineups by the way?