Use rbenv

List all available versions

rbenv install -l

Install Ruby 2.2.1

rbenv install 2.2.1

Uninstall Ruby 2.2.1

rbenv uninstall 2.2.1

See installed versions

rbenv versions

Set global version

rbenv global 2.2.1

Set local version

rbenv local 2.2.1

An alternative is rvm.

Resources and References