How necessary is a contractors license?

[Furrlo Rogers]

How important is it for a contractor doing specialty work (roofing or siding) to have a contractors license. I am looking at a company to do some roofing and siding work on my first property. They have a the adequate insurance and a business license but now contractors license. They informed me that licensing is not necessary for specialty work such as theirs in our state. How common is this and should I look for someone licensed? I am inexperienced and I don't want to make a mistake my first time out.

If this is the wrong place to post such questions please let me know.