You are not right. Roxy FileMan works only with external files (on HDD!) and with all files (pictures, txt, any files). It's a file manager.
If your site config stores images in db, FileRoxyFileman service will be flush images stored in db before load all files and folders in uploaded folder, if you are Developer, you can search keyword "FlushImagesOnDisk" in your project. The problem solved when I changed to file storage in Media setting