You have the wrong Sangokushi game. There are four licensed Sangokushi games on the Famicom:
Sangokushi (no subtitle) from Koei ->SOROM:
Sangokushi II (no subtitle) from Koei ->EWROM
Sangokushi: Chuugen no Hasha from Namco ->N163:
Sangokushi II: Haou no Tairiku from Namco ->N163:
Neither SOROM nor EWROM cannot be used for N163 expansion audio. Only the last two cartridges are suitable, and of course only in their original non-bootleg versions. Also, be aware that Namco usually uses chip-on-board (i.e. black glob) ROMs.