Hanks and Roberts were pictured in posters for "Larry Crowne" riding a scooter without the required head gear.
Although it was just a poster, Spanish traffic laws prohibit "any publicity, in print, audio or video that may incite excessive speed, reckless driving, situations of danger or any other circumstance involving conduct contrary to the principles of the law."
ThinkSpain said Sunday the alleged transgression will cost Tripictures 30,000 euros ($1,394) in fines.
Hanks and Roberts aren't the first Hollywood scooter-riders to be cited by the Spanish traffic police. Singer Shakira was slapped with a 400 euro ($552) fine last year for riding on a motorcycle without a helmet while filming a music video.