ROS is an open-source, meta-operating system for your robot. It provides the services you would expect from an operating system, including hardware abstraction, low-level device control, implementation of commonly-used functionality, message-passing between processes, and package management.
ROS Lunar is available in AUR packages and seems to be working quite nicely although it lacks some simulators of theAUR package, the AUR is complete and seems to have everything functional.
Kinetic packages on the AUR are a work in progress. There are some issues regarding opencv3 that have not been fully resolved yet. That said, installing a metapackage such as AUR or AUR should bring in all required dependencies (see  for the correct order).
Packages are being added on an as-needed basis. Please send package requests to <aur AT seangreenslade DOT com>, and post any issues with the current packages in their respective AUR comments section.
Note that catkin uses python2, and therefore catkin_make may fail unless it it explicitly pointed to the python2 install. To do so, add the following alias to your .bashrc (or equivalent):
alias catkin_make="catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python2 -DPYTHON_INCLUDE_DIR=/usr/include/python2.7 -DPYTHON_LIBRARY=/usr/lib/libpython2.7.so"
Rebuild when Boost is updated
When you update a library that ROS depends on, e.g. Boost, then you need to rebuild all the packages that link to it. You can determine which ROS packages depend on Boost with a command similar to the one below.
export LANG=C;pacman -Qi boost | grep "Required By" | tr " " "\n" | grep -e "^ros"