I have made a savegame structure to pass when it transitions from room to room. That is mainly used to pass state set from room1 to room2. I made this for my big christmas adventure (4 rooms) still to be released this christmas. It involves Santa,Elf, Doc brown (lookalike), Marty Mcfly (lookalike) and a timemachine.
The only thing to do is save that state (groovy struct) to the Libgdx preferences in some sort of json format. It would not be to hard and when making it is in the back of my mind.