To raise the roof is to make a loud noise, especially by cheering, whistling or clapping at a concert or show.
This idiom conveys an image of a building’s roof going up in the air because of the force of a tremendous noise underneath it.
Examples of use:
1. The fans raised the roof with their applause.
2. I think tonight’s show will be a huge success. The audience will raise the roof, I’m sure.
Image by Anirudh Koul under Creative Commons license