In my opinion, the best stats for all three ninjas are +Life and -Res. The reasoning for this is that all three ninjas excels with more HP. Roshi is squishy during the first few rounds, Zetsu's mystery is based on HP, and Kisame is a Tank. The reasoning for -Res over -Def is due to what a wise person once told me (*Cough* Tobei), Defence is more valued over Resistance because the majority of frontal attacks are standard attacks, which are usually Taijutsu oriented, thus -Res over -Def.

~Jib