The Angels optioned first baseman/outfielder Efren Navarro to Triple-A Salt Lake to make room for Roth.
"Just to get through today and tomorrow, we're going to need a little bit of length and Michael can provide it whenever it's needed," Angels manager Mike Scioscia said. "Right now, Efren's a guy who was one of the very few moves we could make to get Michael up here. We need to keep the pitching depth for today. We'll reevaluate things after the day."
Roth threw seven shutout innings on Monday in Arkansas, meaning Saturday was his normal day in the rotation. He was the only left-hander in the Angels' bullpen on Saturday and could flip the platoon advantage against a lefty-heavy A's lineup.
Salt Lake's final game of the season is Monday, meaning Navarro could rejoin the Angels as soon as that day, when the Major League rosters expand for September.
Matthew DeFranks is an associate reporter for MLB.com. Follow him on Twitter @MDeFranks. This story was not subject to the approval of Major League Baseball or its clubs.