What does ROO stand for?

Radio Optical Observatory

Railhead Ordnance Officer

Range Operations Officer

Reserve of Officers - British

Resident Obstetric Officer - British

Richland Operations Office - Energy Research and Development Administration

Romo - NCIC firearms make code (NCIC)

Rondonopolis - Brazil - Airport symbol (OAG)

Rotokas - Language code (ETLW)