It's a combination of their house seasoning and the searing process.

I worked at a Texas Roadhouse for awhile as a grill cook, so maybe I can provide a little insight.

The grill station in the kitchen is set up for 2 people to work; there's a gas grill on either side of a “flat top” stove. The flat top is basically a sear plate that heats up to over 500°. When an order comes in, a steak gets seasoned liberally on both sides, then seared for exactly 1 minute on each side on the flat top. (There's a timer that gets utilized to let the cook know when to flip it.) Doesn't matter the size or the cut of steak, all go through the same process (unless no seasoning is requested, then the sear step gets skipped). After 2 minutes on the flat top, the steak has a nice “crust” on the outside, and it goes on to the gas grill to get cooked to temperature and add the diamond grill pattern. (Sidenote: if your steak at Texas Roadhouse doesn't come out with perfect diamonds seared on it by the grill, either your cook screwed up or they don't know [or care] what they're doing. We took a whole lot of pride in making those grill marks line up perfectly where I worked, and you only get one shot at it.)

After it's cooked to the desired done-ness, the steak is put into a half-window above the grill to go to the next station (the guy behind the grill wall). Their job is to put the steak on the right sized plate and put the correct sides on. They're supposed to wait between one and two minutes before taking the steak from the grill window and plating it to allow it to rest properly. The plate then gets shoved to the next station, where whole orders are assembled (which could be from grill, fry, or salad stations). All the plates are put on trays and a “food runner” is called for to bring the order out to the appropriate table. Tray assembly to table run takes about 1 minute as well.

So… that steak that tastes so damn good has been seasoned, seared, grilled to temperature, and allowed to rest for 3 or 4 minutes before hitting your table. Their house blend seasoning is delicious, and getting the proper cooking technique makes it all the more perfect. If your local Roadhouse employees take pride in their jobs (we definitely did), they can put out a steak that rivals some MUCH more expensive restaurants.