I was at Brasserie19 a week or so ago on a Thursday night. The dinner/couples crowd started clearing out by 9 or so and I lost track of the Ferrari, Lambo, Aston, Bentley pulling up to the valets after that. Benz, Rover, and BMWs didn't get a 2nd look and got parked in the back. Some looked like young posers, but they were pulling up in $100k+ cars so they knew how to strike a pose well. I was questioning if some of the ladies were high-end providers.
Yes, ROAK is home of the $1000 millionaires as someone else put it, but it was ok for what it is.
I know a few low-key spots in Houston, however they aren't clubs. One is Mr. Peeples, they have amazing food and I love the atmosphere. They have really great bartenders and they are supposed to be building a club in their lower level soon. Another spot, is kind of a hidden gem is Zimm's Martini & Wine bar. It's a really low key, sexy place, with amazing drinks as well.
Second (or Third) that Roak is douche-tacular. Houston has, if anything, more of this sort (what in Dallas or Miami they'll call '$30K Millionaires', except here it's so bad I'll call them $15K Billionaires). Avoid like the plague Roak or St. Genevieve. Absolutely brutal.
Bra19 likely is the well heeled crowd, given how close it is to river oaks, but I'm sure there are a lot of fakes there too.
If you're looking for clientele, I've heard that Mo's steakhouse in the Galleria is a place that wealthier guys will be looking to meet providers.
Overall though, there's definitely a lack of "elite" places in Houston - or (like River Oaks Country Club) one doesn't easily get admitted.