For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:fritzbox:RogerRouter/openSUSE_Slowroll/home:ecsos:fritzbox:RogerRouter.repo
zypper refresh
zypper install ninja
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:fritzbox:RogerRouter/16.0/home:ecsos:fritzbox:RogerRouter.repo
zypper refresh
zypper install ninja
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:ecsos:fritzbox:RogerRouter/15.6/home:ecsos:fritzbox:RogerRouter.repo
zypper refresh
zypper install ninja