The engine suddenly 'roared (back) to life'. [=it made the loud sound of an engine and began running well]
The audience 'roared' with laughter. [=the audience laughed loudly for a long time]
The fans were 'roaring' [=yelling and cheering loudly] after their team scored.
(..) - It's the thessalhydra, I'm telling you. It's not the thessalhydra. I'm telling you, it's the thessalhydra. The thessalhydra! - Damn it. - It roars in anger! - Will, your action! - What should I do? I... Fireball him! Fireball the son of a bitch. Fourteen! (..)2016 TvShow: Stranger Things Title: Chapter Eight: The Upside Down Season: 1 Episode 8