Short answers, pulled from the story.
"Roar" was co-written by Katy Perry, Bonnie McKee, Dr. Luke, Max Martin, and Cirkut in March 2013. Perry has said she wrote the song after undergoing therapy, when she felt tired of keeping feelings inside and not speaking up for herself.
"Roar" was released on the 10th of August 2013, by Capitol Records as the lead single from Perry's fourth studio album, Prism. The song leaked two days earlier than its scheduled August 12 release date.
As of November 2019, "Roar" has sold 15 million copies worldwide. In 2013 alone, it sold 9.9 million combined sales and track-equivalent streams globally, ranking fifth among all singles that year according to the IFPI.
The music video for "Roar" was filmed at the Los Angeles County Arboretum and Botanic Garden over three days, from August 7 to the 9th of August 2013. It was directed by Grady Hall and Mark Kudsi.
"Roar" reached number one on the Billboard Hot 100 for the chart dated the 14th of September 2013. It spent two weeks at the top before being succeeded by Miley Cyrus's "Wrecking Ball", and became Perry's eighth number-one single on the chart.
When "Roar" was certified Diamond by the RIAA in June 2017, Perry became the first artist in history to have three Diamond-certified singles in the United States. The other two are "Firework" and "Dark Horse".