If the roof of your house is old and damaged, you really need to talk to a professional roofer, who, after a careful inspection, will tell you what is the best course of action: repair or replacement.
When it comes to an old roof, which has exceeded its warranty period as well as the estimated lifespan, you will most likely be recommended to replace it.
That doesn’t mean that the roofers that make this recommendation do not want to deal with it anymore and they want to sell you a modern roof; it is not about that, but about the fact that repairs to an old and degraded roof are no longer effective. You will pay money for results that will not last, which is definitely not the best thing to do. The roof will break down again and, in addition, it is hard to believe that it will be able to provide the protection and energy efficiency you need.
Therefore, it is best to contact a licensed San Mateo roofing company and trust its professional advice, even if the idea of replacing the roof is anything but appealing to you. Be sure that you will not become more excited about it in the future, so do not postpone an inevitable thing, on which your safety and comfort depend.