There are several reasons why it’s worth it to hire a professional roofer instead of attempting it yourself. The first is safety. Roofing is inherently dangerous, as a fall from a roof could seriously injure or kill you. Roofers have specialized equipment and training to help prevent accidents.
Next is experience. Roofers know how to spot problems (leaks, missing shingles, moss or mold growth, etc.)  in your roof that could potentially save you from costly repairs down the road.
And finally, roofers save you time by getting the job done quickly and with a high degree of quality.