Ok… being a total Apple newbie… and the original poster I have literally just got this to work. I was under the assumption that your phone and its contents were linked to 1 Apple ID and more importantly if you change the Apple ID on the phone, it wiped the contents and replaces it with the content of the ‘new’ Apple ID.
This I found is not the case doing it as below:
1: So I downloaded the Roomie App + all in app purchases via my iPad App Store ( My Apple ID)
2: Then on my wife’s iPhone I changed her Apple ID to my Apple id.
3: Went to the App Store on the phone, searched for roomie remote. The App no longer has a price showing but says ‘Install’. So I installed it.
4: Opened the Roomie app and proceeded to the In app store to update the inapp purchases.
5: App is now fully installed
6: changed my Apple ID back to My wifes ID
7: Setup now complete
So this is all you have to …