Answer:
The best scenario would be reaching an agreement between the seller and the buyers that is consistent with terms of the contract.
The woman told his agent that she would remove the roses, but the agent apparently did not tell the customers that these roses would be removed. In that case, it's best to check if there is any written document that specifies that the roses would be removed prior to the selling of the house. If there is, then, the customers will have to either accept the conditions, or look for another house.