"That very first pitch you have to be right on," Roth said. "You're coming in with men on base maybe, so that first pitch means something right away. I learned that last year."
After starting 14 games with Double-A Arkansas, Roth was called up to the Angels on Saturday to bolster a bullpen that now has two left-handed arms. In 2013, Roth appeared in 15 games for the Angels during three separate stints and posted a 7.20 ERA in 20 innings.
"Last year was kind of a learning year for me, learning what I need to do to be prepared to come out of the bullpen versus being a starter," Roth said.
Roth dazzled in Arkansas, going 7-4 with a 2.40 ERA in 90 innings.
"He's definitely found his rhythm and delivered and he's having a great year down in Double-A," Angels manager Mike Scioscia said. "We know his makeup is great and, hopefully, it'll translate into when he gets an opportunity up here to have better results."
Roth, 24, last started on Sunday for Arkansas, tossing six innings of one-run ball.
Reliever Cory Rasmus was optioned to Triple-A Salt Lake to make room for Roth, who made his season debut in Saturday night's 11-5 victory. Roth picked up the win after tossing two perfect innings with two strikeouts in relief of Hector Santiago.
Matthew DeFranks is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.