On a sidenote, the Naked Fanatics are big crazy dudes with 2 hp's who are on drugs, literally. I hear that you should just get them with a bunch of slingshots and javelins before the melee, than repeatedly flank them with your cavalry. Ibrahim made a guide in the gameplay section about how to properly utilise cavalry to their full effect.
Yes. Try and pin them with something heavy, like Principes or Triarii [haven't played Romani in a while, so my ideas of heavy might be off, heh]. Circle around with Velites/Rorarii/Hastati, and throw some javelins in their back. Then charge with heavy cavalry [Equites Romani/Equites Consulares/Equites Extraordinarii]