So.. An individual have the license but do everyone else who is working on the project needs one too?

-Or an individual need one only



I live in CaliforniaThanks for updating and providing the trade.



The State of California requires that anyone who contracts to perform roofing services exceeding $300.00 (including labor and materials) must have a valid California State Contracotrs License.



The contractor needs to have a C-39 Roofing or B General Contractors license.



Employees are not licensed, many contractors will "subcontract", these contractors would also be required to have contractors licenses, but often run afoul the law.



See the website of The Roofing Contractors Association of So Cal.
For roofing, I think only the contractor needs a license, mostly for business reasons. Individual practitioners may need safetly training certificates though.



Trades such as Plumbing, refrigeration, welding, gasfitting, and elecrical, usually require each practitioner be individually certified for that trade.
You need a licensed practitioner for each specialty to

supervise and take responsibility for, that work.