They don’t usually release new batches of FPs, except when they change park hours. And given you’ve just been booking, I assume you’re going when RotR is due to open. So they might extend park hours.
If they do, they will release FPs for those extra hours usually within 24-48 hours but it can be earlier such as 12 hours after they extend.
The quickest way to find out about extended park hours, short of checking several times each day, is to subscribe to Touring Plans and setting up your trip on your dashboard. They will then email about any changes and you can be ready to check for extra FP times.