The game had been postponed by rain Wednesday.
The Gamecocks (47-18) play again Thursday night against Arkansas. They need two wins over the Razorbacks to advance to the championship round that starts Sunday.
Grayson Greiner and Chase Vergason hit consecutive RBI singles in the second inning to erase Kent State’s 1-0 lead. LB Dantzler homered in the third against Tyler Skulina.
Kent State (47-20) finished 1-2 in its first CWS appearance.
Roth (9-1) struck out eight and walked none. He retired 22 in a row after giving up Sawyer Polen’s RBI single in the second inning.
After Wednesday’s rainout, South Carolina coach Ray Tanner decided to give the ball to Roth instead of scheduled starter Jordan Montgomery.
Roth, working on four days’ rest, continued to stamp himself as one of the most dominant pitchers in CWS history.
The senior left-hander became the first CWS pitcher to throw a complete game with two hits or fewer since June 6, 1993, when Mike Fontana of Long Beach State threw a two-hitter against Kansas.
Roth also became the CWS’ all-time leader in innings pitched, with 53 2-3 over three years, and tied a CWS career record for starts with his seventh.
The second was the only inning in which Roth allowed a baserunner. After Polen’s single, he got Nick Hamilton to hit into a double play.
The game lasted just 2 hours, 7 minutes, making it the shortest at the CWS since 2003 when Rice and Missouri State played in 2:02.
Kent State had entered the game having won each of Skulina’s last 12 starts. Skulina (11-3) left with two out in the sixth after allowing four runs on six hits and four walks. He struck out nine.
Roth earned his second win of the CWS. He pitched 6 1-3 innings in a 7-3 victory over Florida on Saturday.
In 11 career NCAA tournament starts, Roth is 8-0, pitching at least five innings each time and never allowing more than three earned runs.
Kent State shut down South Carolina’s offense after Dantzler hit his 10th homer of the year in the third. Skulina, Casey Wilson and Brian Clark held the Gamecocks to one hit the rest of the way.
South Carolina will become the first team since Georgia in 1987 to play all or part of two games in the same day at the CWS. The last team to play two full games on the same day was Michigan, on June 2, 1980.