Moronta, the club's No. 27 prospect per MLBPipeline.com, began the seventh, allowing one run on two hits in two-thirds of an inning and striking out one.
"He had some horrible luck, didn't he?" Bochy said of a bloop single by Nolan Arenado that put Moronta in a jam.
Gomez retired Trevor Story on a line drive to right field to end the seventh.
"Both of them had great stuff," Bochy said.
Asked if his appearance was a fun experience, Gomez said through an interpreter, "It wasn't as much fun as you might think. I went out there and took it seriously."
Bochy indicated that Gomez (3-9, 4.07 ERA in 38 games at Triple-A Sacramento, including 13 starts) will be used in long relief. Moronta (3-1, 2.92 ERA with five saves in 34 games at Sacramento, Double-A Richmond and in the Arizona Rookie League) will appear in shorter stints.
"We need to take a load off guys," Bochy said. "The last thing we wanted to do was run short [of pitching] in September."
Bochy said that Slater, the club's No. 6 prospect, who recovered rapidly from a right groin strain that he sustained on July 7, will probably play every other day, as a precaution. He hit .290 in 29 games with the Giants before his injury.
To accommodate the additions to the 40-man roster, the Giants designated outfielder Carlos Moncrief for assignment.
Despite ranking among the Giants' leading prospects, outfielders Chris Shaw and Steven Duggar were not included in the final round of roster reinforcements. That's largely because the Giants have more ambitious plans for each of them -- more than receiving a handful of pinch-hit appearances and an occasional start in September.
Shaw and Duggar are the club's Nos. 2 and 7 prospects, respectively. Further reflecting their value, the pair will participate not only in the Arizona Fall League, but also at the Giants' instructional league camp. Both missed significant playing time with injuries this season.
In Shaw's case, working overtime will help him continue his transition to left field from first base. The Giants are less worried about Shaw's hitting, which included 24 home runs between time at Sacramento and Richmond.
"Those guys are on the radar," Bochy said.
Chris Haft has covered the Giants since 2005, and for MLB.com since 2007. Follow him on Twitter at @sfgiantsbeat and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.