When saying everybody who entered the room left by 11.45 with the exception of the victim, all of these people left using the front door! I should also clarify, given the next statement:
By this, I meant: Dr. Snell’s keycard remained on his person at all times that day up to and including 11:45; the “within the living room” part was actually meant in context of where he was then (dead, when his body was discovered). It doesn’t mean all day, since he was at the university with his keycard just a few hours earlier. Furthermore: “with the exception of the victim” in the previous Red shouldn’t be taken as a further Red Truth the victim was present in the room at 11:45, but rather a Red that “the victim is not necessarily bound by this Red” and thus could be in the room. Figured that should be cleared up, given the possible misunderstandings I was seeing.
Now, on to the rest:
The roof access door is always locked unless the keycard is swiped, at which point the door remains unlocked until closed, where it will auto-lock. It can be opened from the roof-side even if locked; however, that did not happen at any point on the day of Dr. Snell’s murder, June 19th (henceforth, “June 19” and “the day of Dr. Snell’s murder” refer to the same day).