polyurethane foam

I have a roof that resembles the surface of the moon.Can you coat this?Is there a membrane application that i can offer a warranty?can you smooth the surface first..there is alot of blistering and bubbling

You say:- "Is there a membrane application that i can offer a warranty?" Are you a roofing contractor or a customer?

If you are a contractor then you should refer it to a firm that is familiar with SPF because being unfamiliar with it you will be wasting your time and the clients money. A SPF roof that has not suffered too much UV degredation can be repaired. Blisters can be removed, scarfed new foam applied if necessary pressure washed and re-coated. The fact that your roof "resembles the surface of the moon" does'nt mean it's shot, it likely means the applicator/s applied it when there was too much moisture present (rain/dewpoint).

Yes it is possible to "fix" the roof, it's also entirely probable that it isn't. Key to your question is What is a cost effective solution. Where are you located? How old is the roof? How big is it? Have any of the blisters broken open? Pics would help.

Do you see yellow foam, or is the current coating intact?

Kev, if it is all bubbled and blistered, coating is going to be a waste of money. If it is not adhered to the original surface, wht makes you think it will stay adhered once you put a coating over it? As far as going over it with a one ply and smoothing it out, good luck. you will find that in places it will be loose and come right off, but in others it will take a ton of time and effort to break it free. I have never been sucessful in "Leveling" off a sprayed urethane roof.

It might be easier to strip off the roof including the original roof beneath to see what the deck looks like and to get a clean surface. That is what the "big contractors" would do. good luck!