gz-msgs : Messages for Gazebo robot simulation ( https://github.com/gazebosim/gz-msgs )
gz-transport : Transport library for component communication based on publication/subscription and service calls ( https://github.com/gazebosim/gz-transport )
Add an ebuild in portage :
The ebuild is now in the portage tree.
You can also use layman : emerge layman then layman -a ros-overlay
For Paludis use this rsync : rsync://gentoo.zugaina.org/ros-overlay-portage
If you have a problem : ycarus(-at-)zugaina.org