Festival goers have the chance to meet Britain's Owen during a “meet the audience” event being held at Rome’s auditorium on Saturday evening.
The actor was spotted in the capital on Thursday enjoying an ice-cream with his eldest daughter, Celebritybabyscoop.com reported.
The Knick, a film by directed by Steven Soderbergh and starring Owen will be screened on Friday night.
Costner, who stars in Mike Binder's Black and White, will also give a talk as part of the festival’s “conversation” series with actors and directors, Ansa reported.
This year’s line-up of films includes 24 world premieres, such as Aleksey Fedorchenko’s drama Angels Of Revolution and German thriller The Lies of the Victors.
English-language screenings include the European premiere of Stephen Daldry’s Trash and Gone Girl, by David Fincher.
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The prizes this year will be decided by a vote by the viewing public as organizers move to cut costs by doing away with expensive star juries.
Under the novel system, festival goers will receive tickets with a code enabling them to vote online for the five main prizes, previously handed out by a committee of industry insiders who had to be fed, watered and lodged over the course of the festival, at considerable expense.