I read this from time to time and I don't get it. This is literally what I do on Ubuntu LTS:
sudo apt-get install build-essential openssl-dev zlib1g-dev
wget http://ftp.ruby-lang.org/pub/ruby/2.0/ruby-2.0.0-p0.tar.gz
tar xvfz ruby-2.0.0-p0
cd ruby-2.0.0-p0
./configure && make && sudo make install
This is not hard, and it's never caused me any kind of trouble.