The phrase "roar of laughter" is often used to describe a loud and boisterous laughter shared by a group of people. However, there are plenty of other ways to describe this type of laughter. For example, you could say that people were chortling, guffawing, chuckling, or cackling. Other options might include shrieking with laughter, hooting, or howling. Each of these phrases conveys a slightly different tone or level of intensity, but they all capture the idea of a group of people enjoying a humorous moment together.