From my understanding in the chinese version the jinchuuriki ninjas are the counter to the kage ninjas, at least that is what I have heard if you already have 3 rares I would save since Roshi is a game changer and he is like 200-300 seals scrolls. Not exactly sure, but he is the super rare. I would save, but it's your choice. We don't know how long untill the new treasure is released. It could be in a month or maybe even in 4 months, but at the rate we are progressing I would assume 2-3 months.