Note sure if this has been posted yet (searched and didnt find anything). Found this on gamefaqs though.
So apparently each race has a noise in the sound files for /roar, they just haven't been implemented in the actual game yet. That said, please enjoy copying and pasting these scripts into your game:
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsDwarfFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsDwarfMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsGnomeFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsGnomeMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsHumanFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsHumanMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsNightElfFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsNightElfMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsOrcFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsOrcMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsTaurenFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsTaurenMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsTrollFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsTrollMale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsUndeadFemale.wav")
/script PlaySoundFile("Sound\\Character\\PlayerRoars\\CharacterRoarsUndeadMale.wav")
/script PlaySoundFile("Sound\\Character\\BloodElf\\BloodElfFemaleRoar01.wav")
/script PlaySoundFile("Sound\\Character\\BloodElf\\BloodElfMaleRoar01.wav")
/script PlaySoundFile("Sound\\Character\\Draenei\\DraeneiFemaleRoar01.wav")
/script PlaySoundFile("Sound\\Character\\Draenei\\DraeneiMaleRoar01.wav")
The draenei male one had me loling, and the draenei and blood elf female ones seem more like /charge emotes.