I use Sound Alerter and Gladius for arena.
/roar does have a sound and it does something like " arghhhhh " or idk i dont remember exactly.
Disable those addons and see what happens.
The sound files for /roar are there, but Blizzard didn't put them into use until 4.2 it seems. (Limited research)
Code:
/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")