There’s a photo in the FAAM collection which is reproduced on p.38 of my book on the Skua and Roc (MMP 2007) which shows a close-up of the markings on the side of Roc RO-150. This shows a rough swastika-shape on the white disc, slightly darker than the disc itself, which isn’t visible on the wide shot. This suggests to me that the swastika was applied then painted over in distemper for the transit flight.