With iOS 14, the authorization to give access to Photos to an app got a little more complex. It's good for privacy but the question asked is a bit confusing.
So, if you choose to give access to "selected photos". You will have to go through two images picker every time you use PhotoRoom.
Our recommendation is to select "All photos" as it will make the PhotoRoom experience much better. To change your preferences to all photos, you can do the following.
Open the Settings app
Search for PhotoRoom
Select All Photos
Here is a demo