Romo connected on 23-of-30 passes for 284 yards, hooking up with Williams five times for 117 yards as the Cowboys (1-2) got a much-needed win after starting the year with two disappointing losses.
The Cowboys were able avoid their first 0-3 start since 2001 with the victory over the Texans (2-1).
Houston was led by Matt Schaub, who tossed for 241 yards. He completed 23-of-32 attempts with one touchdown and two interceptions.
Arian Foster ran the ball 17 times for 106 yards in the Texans' loss.