FranklyCheck the licence at the source
Take the licence number from the estimate to cslb.ca.gov and confirm it is active, carries the C-39 roofing classification, and matches the business name on your contract. A salesperson representing a licence they do not hold is the single most consequential thing you can catch in one minute.
Compare scope, then compare price
Ask every bidder for the same five items in writing: layers removed, underlayment product, flashing replaced versus reused, ventilation changes, and a per-sheet decking allowance. Once those match, the price difference is a real price difference.
Do not exceed the legal deposit
California caps home improvement down payments at $1,000 or 10 percent of the contract price, whichever is less, requires written contracts above $500, and gives you three days to cancel. These are your floor, not a starting point for negotiation.
Ask about the crew and the warranty holder
Find out whether the crew is employed or subcontracted, who supervises the tear-off, and which entity stands behind the workmanship warranty. A warranty from a company that does not employ the installers is worth understanding before you rely on it.