What kind of roofing is best for my home or business?

It depends on the design, location, use, and several other factors which should be discussed between you and your roofing professional.

What is the difference between an "authorized" installer and a "certified" contractor?

An "authorized" installer simply has permission to and can install a product at their own and your risk. A "certified" contractor has been trained by the manufacturer, schooled, tested, and proven by hands on practical application that they are acceptable as a partner in the application of roof systems that qualify to receive exceptional warranties backed by the manufacturer for up to thirty years and such warranties are supplied on bonded agreements.

Why do I need to ask for proof of insurance, and then call the agent to verify that the contractor is in fact insured? Doesn't the city/state protect me? Should I accept the contractor's copy or word?

As adults we are responsible for our own actions, safety, planning, etc. Even though you may be told or a document may state "insured" always check. The saying "trust, but verify" rules so call and be certain.

Should I be in a hurry and worry I may not get the work done if I don't sign a contract quickly?

NO! Rather the opposite. Slow down, think, and be smart. Don't be pushed into a quick decision or a cheap price. Good work takes time and good money so ask questions and check reputable references and others you trust.

You don't buy medication, groceries, vehicles, and other important items from door to door salesman and you shouldn't buy your roof that way. If there are offers to pay you money, give great refunds or deep discounts or absorb your deductible on insurance funded projects, it is too good to be true and may be illegal.