You can save a lot of data to a text file. The easiest way I've found is to write a single line for each value, and read a single line for each value.

But don't do this. Don't use a text file to carry data back and forth between rooms.

Like Mr-Magnus says above, a persistent controller object (or objects) is what you want. You could make the character objects themselves persistent, and have room, sensitive behaviors for them ( if room = x, run this block of code, if room = y run that block of code) or you can have a persistent controller object that runs various functions in each room act as a courier. Another option, one I like for various reasons, is to have a courier object. Create it before you change rooms, have it grab all the data you want to carry across, go to the new room, apply the data to the necessary objects, and then destroy the courier. When it's time to go back, do the same process again.