Workers' compensation is the nation's oldest social insurance program: It was adopted in most states, including California, during the second decade of the 20th century. The workers' compensation system is based on a trade-off between employers and employees. Employees are entitled to receive prompt, effective medical treatment for on-the-job injuries or illnesses no matter who is at fault and, in return, are prevented from suing employers over those injuries.
As a result, California employers are required by law to have workers' compensation insurance, even if they have only one employee. And, if your employees get hurt or sick because of work, you are required to pay for workers' compensation benefits. Workers' comp insurance provides six basic benefits: medical care, temporary disability benefits, permanent disability benefits, supplemental job displacement benefits or vocational rehabilitation and death benefits.
The vast majority of workers' compensation claims are resolved without any problems. However, sometimes a disagreement can arise between you and your employee over issues such as whether the injury was sustained on-the-job or how much in benefits they are entitled to receive. When a dispute like that arises, the Division of Workers' Compensation can help resolve it through its Information and Assistance Unit or by going before a judge at one of the division's 24 local offices.
Please be advised that if you are a roofer and don't have any employees, you are still required to carry workers' compensation insurance.
If you are an out-of-state employer you may need workers' compensation coverage if you have any employees regularly working in California, or if you enter into a contract of employment here. * From dir.ca.gov site.