Yes, if you ever wonder whether you should disclose, then you probably should. We, in CA, disclose anything that is material affecting the property for sale. .
You should let the buyer know and also tell her when the repair is scheduled and give her the receipt and notes from the repair person immediately after it is completed. If the repair person can not come before the close of escrow date, you can withhold some money in escrow until the repair is completed.
There is a rule of thumb in Real estate...disclose, disclose, disclose...then it's not a problem.
Just ask your Realtor. If you don't have one...I guess you take our word for it, but ths is not legal advice.
BTW, work completed during escrow needs to be by professionals. show the buyer, get a warranty and a receipt.
In CA you'd have to disclose any known material defects and also any repairs that you have made to fix known problems. If the problem arises after the inspection period, you still have to disclose it. A good rule of thumb is, if in doubt , disclose. Put yourself in the shoes of the buyer (and soon you'll be a buyer) and ask yourself if you'd want to know about the problem. The only reason not to disclose something is fear that the buyer may no longer want to buy the property and if you think that disclosing the problem would have that possible result, that's even more a reason to disclose because any problem that might influence the buyer's purchase decision is a material fact. In the end it's up to the buyer to decide what's material to him/her. It's not up to the seller to make that determination. I can assure you that a roof leak is a material fact and the fact that you'll fix it does not change that. I hope this helps.