/usr/include/libroutermanager/ is in libroutermanager-dev 1.8.14-2+b3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libroutermanager/action.h
/usr/include/libroutermanager/address-book.h
/usr/include/libroutermanager/appobject-emit.h
/usr/include/libroutermanager/appobject.h
/usr/include/libroutermanager/audio.h
/usr/include/libroutermanager/call.h
/usr/include/libroutermanager/connection.h
/usr/include/libroutermanager/contact.h
/usr/include/libroutermanager/csv.h
/usr/include/libroutermanager/fax_phone.h
/usr/include/libroutermanager/fax_printer.h
/usr/include/libroutermanager/file.h
/usr/include/libroutermanager/filter.h
/usr/include/libroutermanager/ftp.h
/usr/include/libroutermanager/gstring.h
/usr/include/libroutermanager/libfaxophone/
/usr/include/libroutermanager/libfaxophone/fax.h
/usr/include/libroutermanager/libfaxophone/faxophone.h
/usr/include/libroutermanager/libfaxophone/isdn-convert.h
/usr/include/libroutermanager/libfaxophone/phone.h
/usr/include/libroutermanager/libfaxophone/ringtone.h
/usr/include/libroutermanager/libfaxophone/sff.h
/usr/include/libroutermanager/logging.h
/usr/include/libroutermanager/lookup.h
/usr/include/libroutermanager/net_monitor.h
/usr/include/libroutermanager/network.h
/usr/include/libroutermanager/osdep.h
/usr/include/libroutermanager/password.h
/usr/include/libroutermanager/plugins.h
/usr/include/libroutermanager/profile.h
/usr/include/libroutermanager/router.h
/usr/include/libroutermanager/routermanager.h
/usr/include/libroutermanager/settings.h
/usr/include/libroutermanager/ssdp.h
/usr/include/libroutermanager/voxplay.h
/usr/include/libroutermanager/xml.h