In MA, I've never used or seen a clause like this even on larger commercial jobs. It may very well be a state specific requirement.
My WC insurance is for injuries to any of my employees as well as any bystander who might get hurt trying to assist us. Since I've elected not to be included, my WC does not cover me. Instead I have a disability policy for my personal coverage both on & off the job site. Some states such as MA allow company owners to not carry WC on themselves. You want to be sure that anyone including the company owners are covered for personal injury while on your work site.
The liability insurance covers things like a ladder or piece of equipment damaging yours or someone else's property. This would be things like a ladder falling over & smashing into your car.
I imagine that the "The Owner(s) shall maintain full fire insurance for fire protection and extended coverage to cover both the owner and Contractor" is to make sure that you have the property including the materials being used by but not yet billed to you during the construction phase of the work. It covers things like the roofing supplies that are on site that get ruined by a fire before the contractor has been paid for them. It would not cover them if the fire was caused by the roofing contractor or his employees. For instance if he was installing torch down roofing & started a fire. His insurance would cover the damaged materials as well as any damage to your property.
Occasionally if I'm doing a project that has some unusual item of value that we will be working near, I have my agent add a rider just to cover it. For example we modified some antique stain glass decorative panels that were each valued at 10's of thousands of dollars. I wanted to be sure that if something happened that I would be adequately covered.
Your own insurance agent should be able to help you better understand what this clause actually means to you.
Once you decide on a company to do the roof, have their agent Email you a copy of their WC & liability insurance. You want to see the start dates & expiration dates as well as the coverage included in the policy. You do NOT want to have the contractor just give you this.