I'm not exactly sure what you're going for from your equipment list. Why are you using a Y-connector? If you want a mono recording from two microphones, you should be able to either record both mics to the same mono track (or pan center and record to a stereo track; not sure how that recorder works but I've used the previous generation Roland 8-tracks, and it should be pretty similar), or perhaps more ideally, record them to two seperate mono tracks that you can mix together as needed in post.
From what you have, you'll need another phantom power supply (one for each mic). Each mic should be connected to a mono xlr-to-1/4" and then to your recorder. Again, you could use the Y-adapter, but with the 8-track, I'd want to just record two mono tracks. You'll likely want this adapter instead
http://backstage.musiciansfriend.co...male-to-1-4-male-mono-adapter/339523000377000 unless your XLR cables are F-F
Oh, and for the "fullness" of stereo, record all your environments/roomtones in stereo. That'll give you the depth you're looking for. For that, however, you still want two mono adapters (I don't know if that recorder accepts a 1/4" stereo cable; the old ones didn't, but used two cables as left and right signals).
As an aside, hooray for Musician's Friend! They have ended up with much of my paychecks over the years!