A Queen of the Romans also became Holy Roman Empress if her husband was crowned Holy Roman Emperor, in the Middle Ages usually by the Pope in Rome during an Italienzug. Most elected Kings of the Romans did, but some never made it that far, and thus their wives only ever achieved the status of Queen of the Romans.
A Queen of the Germanic tribes might ascend to the position of Holy Roman Empress if her spouse became Holy Roman Emperor, usually through a military expedition into Italy. Conversely, some Kings of the Romans never attained that rank, resulting in their wives only being recognized as Queens of the Romans.