The role of business is the efficient creation of wealth, by taking resources and transforming them into products or services. In manufacturing, businesses take metals and plastics, for example, which in their crude states are not very valuable, and transform them into more highly valued cars or computers.
In services, businesses take people or intellectual property and apply them where they have the most impact, like a law firm or consulting agency. Having people, property, or natural resources inefficiently applied decreases their value and creates little wealth; having these unapplied nullifies their value and creates no wealth.
Small businesses employ huge numbers of people. They are essential to cultivating a spirit of independence, risk-taking, self-reliance, and personal achievement. They require hard work, sacrifice, thinking ahead, and dedication -- all qualities worth cultivating in society.
Without businesses, you can't have any sort of a free market economy. In addition to what the previous post said, businesses also tend to provide the innovation that makes an economy grow. For example, it was businesses that developed the idea of the assembly line that makes modern industry so efficient.
Businesses have a huge role in the economy. Providing jobs is just one of the many necessary parts that business plays in any and all economies.
Businesses also serve as the access points of goods and services, either giving citizens an opportunity to buy the things they need or providing essential services like plumbing and construction.