The autoproj package set that defines all that is needed to run Gazebo on Rock
While the package set does define a source package for gazebo, it's really hard to keep it up to date, given how quickly gazebo itself evolves. The recommended method of installation is to use OSRF's APT packages listed on the Gazebo website.
The package set currently selects Gazebo 8, which requires the APT source above.
You can override this choice in your own build configuration by adding an
autoproj/overrides.d/gazebo-default.osdeps file. You will need to pick the
corresponding sdformat version at the same time, e.g.
gazebo:
osdep: gazebo7 # or gazebo8, …
sdformat:
osdep: sdformat4 # or sdformat5, …