When you say that you "want to be able to see the data before I open the room"... not a lot would be happening before you enter said room, anyway, right? Unless, of course, you're declaring global variables in any room aside from the first one. If that's the case, I urge you to reconsider that.
Having declarations of global variables spread out across multiple rooms can easily lead to adding various pitfalls to your game which may limit you or trip you up later on. For example, if you store any data structure indices or other dynamic resources in a global variable, it implies that you should not return to the room it happened in during the run time of the game (unless you're using a Game Start event, but that would only work in the first room anyway). Doing so would cause a memory leak, unless you include code that checks whether the globals have already been declared... but that's just additional hassle that you shouldn't force yourself to have to deal with.
I personally prefer "init room"-type setups as mentioned by
@Mike - way less error-prone and no hidden pitfalls. Once you leave it, there will be no sane reason to ever return to it, anyway, so you don't have to give it any second thoughts.
