Factual error: As has been noted, the problem with pressure differentials will make it impossible to flood someone's room with CO2 from sublimating dry ice anyway, but there is another problem. Dry ice sublimates at -78.5 C. That gas is going to be very, very cold and it will rapidly bring the temperature of the room down to a very uncomfortable level. Before a sleeping person suffocates they would be woken by the freezing cold.
Factual error: The murder kills the two students by drilling a hole through the adjoining wall of the victim's room at floor level, placing 40lbs of dry ice next to the hole, and allowing the sublimating carbon dioxide to pass through the hole into the victim's room and creating a toxic atmosphere. Since the two rooms are at the same air pressure, the only possible way for the CO2 to move from one room to the next is to be pumped through. As neither room has an excessive level of carbon dioxide in the atmosphere the sublimating gas would fill both rooms until the CO2 levels in both rooms was the same.
Plot hole: How did the occupant of the room where the dry ice was placed only burn his index finger when he picked it up? His thumb, other fingers, and palm were all undamaged. Was he wearing special gloves that had only the index finger missing when he picked up the dry ice?
Plot hole: The bodies were pink because of exposure to the lower temperatures created by the dry ice venting into the room. None of the CSI team noticed a chill when they entered the room? None of them noticed the bodies were cold to the touch? No one noticed that the body or liver temperatures didn't match with the estimated time of death?