RuboCop comes with a set of different formatters that let you control how the results are presented.

If you want to output the result in machine readable JSON;

rubocop --format json --out results.json

The rubocop-sketchup gem provides a custom formatter designed for SketchUp related cops. It explains which cops to focus your attention on.

rubocop -f extension_review -o report.html

See RuboCop's documentation for more examples.