I assume the advice to be at the gate "around 4 or 5 AM" generally applies to weekends, not weekdays.
I was there in June of 2003 on a weekday, got to the gate shortly after 6am and made it in with no problem, to say the least. Not sure if the Roaring Brook parking lot even filled up that day (but don't bet on that).
And we were up there in 2002, in August, again on a weekday and made it in easily. I think the gate opened at 5am that day, but I can't remember. We were stormed off the mountain high up the Slide Trail, unfortunately, so I had to go back this year.
But, travelling alone this year, I felt free to hike Knife Edge on my way to the summit. Big fun.
Point is, I don't think you have to show up an hour or two before the gate opens, on a weekday. Might have to on a weekend, though.