Nope. You need to do the following:
1) Catch Regirock. You do so by walking 6 steps down and 9 steps right from the panel near the door at the top. Press A. Enter the ruins and catch Regirock.
2) If you have Black 2, you will get an Iron Key when you catch Regirock. If you have White 2, you must receive an Iron Key from Unova Link. After you have the Iron Key, go to Unove Link and change the settings for the Underground Ruins to be the Iron Key.
3) Return to the Underground Ruins and catch Registeel.