What questions should I ask roofer when asking them to fix or replace my roof?

Need to establish that he allows a cost for replacing the deck in case the existing has water damage; plus could be good opportunity to add insulation between the joists if there is none. Consider the condition of flashings, fascias and gutters, replace if in poor condition. Ask if his roof has independent warranty cover and for how long. Hope that helps

Remember to ask how many layers , i install a 3 layer system always an SBS mineral cap sheet better quality. You could also install a single ply roof i.e Firestone rubber or even a GRP fibreglass, also ask him for referrals from previous flat roofing work. Any good roofer will be able to provide this information, if he shows you a picture portfolio make sure it`s his work and not from a library,i always make sure i`m in my own work photos, hope this help you, Wullie