Rosalie de Hemricourt de Grunne is a witch born in Belgica who fled the country with her family to Britannia when Belgica was devastated by Neuroi. She is based on Belgian World War II ace Rodolphe de Hemricourt de Grunne.

Rosalie is the heiress for two families of earls, one Gallian and one Belgican. She also has the right for Britannian crown, although that relation is quite distant. She has had a long and valiant military service since she fought in the Hispanian military campaign. She has a lot of experience and she has received regular training for a military officer.
When she was Flight Lieutenant she got injured in battle in Britannia, while she was under medical care she got promoted as the commanding officer of 506th JFW. She was under medical care, she was getting close to 20 and getting close to retirement so she thought it would be too difficult and she declined. But since people convinced her that there is no other person of such talent for the job, she was promoted to Squadron Leader and she accepted the position of honorary commanding officer.

She is mild-mannered and gentle. Because she is getting close to 20, she doesn't command the battle. During battle the squadron is mostly commanded by Squadron Leader Wittgenstein, but because Flight Lieutenant Visconti has similar personality as Wittgenstein, their subordinates have to go through many hardships.

(Source: Strike Witches Wiki)