Zeromus is arguably the most dangerous final boss in the Final Fantasy series. FFIV doesn't have any optional "super bosses" like many other games in the series, but Zeromus is just as hard as his predecessors.
Your main concern is Big Bang, which deals tremendous damage to everyone. Rosa should do practically nothing but heal the party round after round, even if they're already in good health. High levels and good equipment are key to winning this fight.
Your main concern is Big Bang, which deals tremendous damage to everyone. Rosa should do practically nothing but heal the party round after round, even if they're already in good health. High levels and good equipment are key to winning this fight.