The install scripts already install ROS for you, these instructions are if you wish to manually install ROS.

For Ubuntu 14.04, you can just follow the normal ROS installation instructions.

For Linux Mint 17.x, the instructions are mostly the same, here are the steps (derived from http://insane-on-linux.blogspot.com/2014/10/installing-ros-indigo-on-mint-17.html):

sudo sh -c '. /etc/lsb-release && echo "deb http://mirror.umd.edu/packages.ros.org/ros/ubuntu trusty main" > /etc/apt/sources.list.d/ros-latest.list'
wget https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -O - | sudo apt-key add -
sudo aptitude install ros-indigo-ros-base

If you get the following error:

ImportError: "from catkin_pkg.package import parse_package" failed: No module named catkin_pkg.package

Make sure that you have installed “catkin_pkg”, it is up to date and on the PYTHONPATH:

$ pip install catkin_pkg

Error:

ImportError: No module named rospkg

Fix:

$ apt-get install python-rospkg
$ export PYTHONPATH=$PYTHONPATH:/usr/lib/python2.7/dist-packages

This is kinda a hack, haven't bothered to figure out how to properly install python-rospkg to the proper python location for indigo

If you get this error:

ERROR: the following packages/stacks could not have their rosdep keys resolved to system dependencies: ardrone_autonomy: Unsupported OS [mint] 

when running any rosdep command, add the flag –os=ubuntu:trusty to the command.