Those two links should attest to Rob Roy's historicity. I used to live in that part of the world. Many of the high passes through the hills were known as routes and hiding-places used by cattle-rievers (or rustlers!). Just about the time I left the area, a statue memorialising Rob Roy was being erected in Stirling. Statue of Rob Roy MacGregor by Benno Schotz, Dumbarton Road, Stirling
While Rob Roy the character is held (generally) in high regard, I fear the statue is not - I leave you to decide!