To get advantage on roshi you need to be quite highpowered in comparison with your usual enemies. Han is better if you are usually weaker than your enemies or with lower initiative. Han works nicely with water main or fire main and if you are in the lower side of your bracket then a team with han, azure fang, gnw or sailor sakura and mei/yagura or gakido could let you win some matches you usually lose.

If you want to reach sage of six paths right now by being f2p you need han, without him is impossible unless you got the luck of the devil and pulled hashirama from packs when was available. Roshi can carry you too but only if you have higher initiative than most of your enemies in superkage rank, otherwise you just get owne, so yes, your impression is right.

Because you have higher initiative than most of your enemies in superkage rank by being a very old server f2p (server 99 or older) or because you are in a server so new that you are still not in cross server circuit or you are not f2p. Your teams loses 100% of the times against an higher initiative mei mabui tenten gnw or an higher initiative root meta team.