Although Satuma-Choshu Alliance is considered as the Ryoma's major achievement, there is also a theory that Ryoma was in fact instructed by Satsuma clan including SAIGO and Kiyotada KOMATSU to work on the achievement for the Alliance (Tadamasa AOYAMA), and therefore there are divided evaluations over what kind of role Ryoma played for Satsuma-Choshu Alliance.
なお薩長同盟については龍馬最大の功績と言われるが、実際には、西郷や小松清廉ら薩摩藩の指示を受けて動いていたという説もあり（青山忠正など）、薩長連合に果たした役割の重要性については評価が分かれている。