Salt Lake starter Caleb Clay allowed two hits and faced only one batter over the minimum through the first three innings.
In the fourth, however, Round Rock broke through.
Luis Sardinas led off with a double and moved to third on Hoying's infield out.
At that point, Bees manager Keith Johnson elected to pull in the infield, hoping to cut off the go-ahead run. The strategy backfired, though, when Ryan Rua's hard ground ball barely eluded Salt Lake shortstop Vance Albitz, making it 1-0.
Asked about his decision, Johnson said: "I saw how their guy was attacking us early in the game and Caleb got the ground ball. But it got through. ... Sometimes you have a hunch and have to play it."
The Express didn't stop there.
Michael Choice followed with an RBI double into the left field corner. He scored on Tomas Tellis' single to center before Chris Gimenez eventually made it 4-0 with a sacrifice fly.
Salt Lake got a run back in the bottom of the fourth when Ryan Wheeler drove in Luis Jimenez with a two-out infield single. But with the bases loaded, Albitz bounced out on a 2-1 pitch to retire the side.
In the fifth, Round Rock bumped its lead to 5-1 when Hoying drilled a long solo home run that stayed just inside the foul pole in right.
From there, the Express coasted to victory behind a superb pitching performance by Ross. Making his first appearance since an emergency start for the parent Texas Rangers, the 25-year-old lefthander allowed eight hits and improved his record to 5-4.
"He did a great job of hitting his spots," Johnson said. "He pitched inside effectively inside. He pitched outside. ... He made a lot of good pitches."
R Round Rock snaps Salt Lake's four-game winning streak with a 5-2 victory at Smith's Ballpark.
• Express starter Robbie Ross Jr. scatters eight hits over eight innings to get the win.
• C.J. Cron goes 2-for-4, but the Bees go only 2-for-11 with runners in scoring position.