Question regarding Roof

I just posted the question below. I forgot to mention that we live in Shrewsbury Massachusetts area. If anyone has reccomendations for companies in this area, it would be really appreciated.

We bought a house couple of years ago. The roof of the house has 3 layers of asphalt (may be). The last layer we believe was put on about 11 years ago. Part of the roof on one side of the house is peeling (which is probably 1/20 of the house) but is not leaking. Also, every now and then we find some peelings from the roof in our yard. Although there is no leakage anywhere. Do you think it is time to get entire roof fixed? What kind of materials is being used, which ones are best, what we should ask the contractor and expect as far as warranty goes. Thanks a lot.