In all, Roth, Montgomery and reliever Matt Price faced three batters over the minimum on the day.
"Jordan followed up what Michael did earlier today, was outstanding. He's had some good games for us this year and this was the best one," South Carolina head coach Ray Tanner said. "We had some pretty solid defense behind him ... but Jordan was special on the mound."
South Carolina (48-18) and Arkansas (46-21) play again, at 8 p.m. CT on Friday, with the winner advancing to face Arizona (45-17) in the College World Series finals beginning on Saturday. The Wildcats eliminated No. 3 Florida State on Thursday, 10-3.
The Gamecocks became only the third team to win two College World Series games on the same day, joining Holy Cross (1952) and Tennessee (1951), and first team to play two full games on the same day since Michigan and California did it in 1980.
Roth, a ninth-round pick of the Angels in this month's First-Year Player Draft, struck out eight and walked none while retiring the final 22 batters he faced.
"Once we scored, it's almost like we made him mad," Kent State head coach Scott Stricklin said. "We scored that run in the second inning and, 'That's not happening anymore.' He was outstanding. ... That's why he's an All-American."
Roth's outing set the tone for Montgomery in the nightcap, as the freshman struck out six and walked one, despite admitting he had butterflies before the game.
"Definitely pitching in front of 20,000 people had me a little nervous in the bullpen," Montgomery said. "But after that first inning, I guess the way I settled in and the way the team was playing behind me, I was just kind of staying on cruise control and just went."
South Carolina scored both of its runs against Arkansas left-hander Randall Fant (29th round, Indians) in the second inning on consecutive doubles by Erik Payne and Tanner English.
Chase Vergason followed two batters later with an RBI single to plate English, who had advanced to third on a groundout.
Vergason's single knocked out Fant, but right-hander Brandon Moore tossed 5 2/3 scoreless innings of relief for Arkansas, which looks to rebound Friday.
"It's win or go home, but it's no different than any other game," Moore said. "We have to come out and play with energy and we'll come out a lot more intense tomorrow."
Roth's gem against Kent State was the first complete game with two hits or fewer in the College World Series since 1993 (Long Beach State's Mike Fontana), and only the fourth time a pitcher had gone the distance while allowing two hits or fewer without a walk.
Thursday's performance was the latest impressive outing by Roth in his College World Series career. The senior left-hander is 4-0 with a 1.34 ERA in nine appearances in Omaha.
Roth set the record for most innings pitched in College World Series history with 53 2/3, passing Ohio State's Steve Arlin (1965-66) and Texas' Greg Swindell (1984-85). Thursday's start also was Roth's seventh in the College World Series, tying him with Miami's J.D. Arteaga (1994-97) for the most all-time.
Stricklin called Roth "the biggest superstar our game has."
"He just knows how to pitch," Stricklin said. "He does everything the right way, great student. I've got a ton of respect for him. I've enjoyed watching him on TV. I did not enjoy watching him today."
No. 8 South Carolina 4, Kent State 1
Arizona 10, No. 3 Florida State 3
No. 8 South Carolina 2, Arkansas 0
Arkansas (46-21) vs. No. 8 South Carolina (48-18), 8 p.m.