OpenStreetMap edits only the map data, not your navigation device. The roundabout is positioned correctly, according to satellite images, so if your device is saying you were still south of the roundabout but you had already passed it, you will need to take this up with the manufacturer of your navigation device. But if you are saying that something specific at your marker position should actually be mapped north of the roundabout, that is a different matter. But we would need to know which specific map feature is wrong in order to correct that.