rooke is the general of the armanda and he is a little hard to defeat but i think these steps might help you
1. attack rooke at all times even in the second fight cause his attack bonus like if he hits you he will hit you untill you die or dodge/block his attack.
2. use these companions at levels like this gracie conrad. 54. el toro 52 bonnie anne is optional 52 ratbeard 55/optianal
3. get help! dont just try soloing off like i did it took me 2 times the second time i fought him cause of his bring you use before magic :I.
I managed to beat both of his fights the first time through.
I think one teeny tiny thing you're missing is DON'T BRING IN ANY MUSKETEERS
Rooke has the Epic "Rookochet" which will immediately deflect any normal musketeer shots towards an ally. Being a musketeer, I learned this the hard way.
If you are a musketeer, either use a shooty/slashy or shooty/stabby weapon (the ones made up of a sword and a gun) or only use your powers (e.g. inferno shot, hurricane round, rain of mortarshells, etc.).