I will be interviewing for roseman as well. The interview day will start at 12 pm and last for about 5 hours. From my experience with two other schools, the time frame they give you is normally very accurate. The school is 30 mins away from the airport and thus you will get there by 5:30 at the earliest, assuming you call the taxi company and remind them to arrive at the school at 5:30 exactly. In addition, if you get your boarding pass online, you'll probably be at the gate by 6pm.
Flights normally board 30 mins prior to departure, so if you book your flight at 6:30 pm you will definitely be pushing it. I recommend at least 7:30 imo