That is a great question for your broker

attorney question

only if unsigned by the seller.

Best bet is to talk to an RE attorney.  This is way above my pay grade.

Two separate contracts, separate issues. Beyond your pay grade. Consult an attorney

You are asking legal questions about contract enforcement and we are not to give advice out of our area of expertise. Ask an attorney.

consult with an attorney.... but you don't need a listing agreement to sell a home!!

Interesting question and answers. 

No idea.

Talk to your broker and an attorney.

I agree with Harry F. D'Elia 

Broker or Attorney question.  

I am no attorney and my advice is worth what you are paying... nothing. My initial thoughts, though, would be:  If I understand correctly, the listing agreement was signed by the seller?   The purchase agreement was signed by both parties?  Just because a contract is voidable does not make it void.  If the seller signed the purchase agreement he/she is bound by the terms of the agreement.  The roof issue should have been addressed within the purchase contract.  

Need legal advice.

This sounds like a question to be put before an attorney for resolution.

yes

Is there an actual issue with one party to the actual ratified contract not wanting to perform?  If so, time to get a real estate attorney involved. The issue with the listing agreement is a separate issue. 

I am sure there are some legal terms that would protect the listing agent.

More of an attorney question, I think.

Do not pass go!  Do not collect @$200...DEFINITELY seek legal counsel!  

Attorneys are not cheap, but they know the relevant case law, if they work in the right field.  That's why you need an RE attorney.  Relevant case law means what courts have decided before, and in courts, they set precedents and most of the time, later court cases follow the same decisions as the earlier ones.  Case law can be helpful to know with questions like this.

Talk to an attorney about contract law.

Suggest you talk to a real estate attorney.

Legal counsel familiar with this type of law for the relevant jurisdiction should be consulted.

I would have the parties involved consult with an attorney. 

I would talk with an attorney about this contract

Look at the terms of the executed contract.

Consult an attorney.     

The seller signed the contract and it sounds like it was ratified. Time to check with an attorney.

This sounds a little convoluted.  Bottom line - do the sellers want to sell to buyers who want buy?

An attny can give you an educated opinion, a judge may be able to give you an answer, we can give you neither.

  Probably not.  Two different contracts, between two different parties.  See an Attorney.