Romo completed 23 of 30 passes for 249 yards.
The win gave the Cowboys (8-6) a half-game lead over the New York Giants in the NFC East. The Giants play today against the Washington Redskins.
The Bucs (4-10) lost for the eighth consecutive time.
Romo threw a pair of 8-yard TD passes to Miles Austin and Dez Bryant in the first quarter, then finished a seven-play, 89-yard drive with a 9-yarder to Laurent Robinson to make it 21-0 with just under 5 minutes remaining in the second quarter.
Austin’s touchdown pass from Romo was set up by Tampa Bay’s NFL-leading 32nd turnover, a fumble by quarterback Josh Freeman on the game’s fifth play.
Romo made it 28-0 on a quarterback sneak in the closing seconds of the opening half.
The Bucs, which had yielded 69 consecutive points dating to the second quarter of last week’s 41-14 loss to Jacksonville, finally got on the scoreboard in the third quarter.
Rookie Adrian Clayborn sacked Romo from behind, forcing a fumble that linebacker Dekoda Watson, a former South Aiken star who went to Florida State, returned 4 yards for a TD for a much-needed spark.
Freeman’s 13-yard TD pass to Dezmon Briscoe and a two-point conversion throw to Kellen Winslow trimmed the Dallas lead to 31-15.
There was no scoring in the fourth quarter.