It might take a while to get there, however.
On the Cardinals' first offensive play of the game, Rosen took the snap from under center at his own 25. The pocket was wide open, giving him time to wait on fellow rookie, wide receiver Christian Kirk, to kick into high gear. In the meantime, veteran receiver Larry Fitzgerald ran a deep crossing route, pulling a safety with him. Kirk made a double move on the cornerback defending him to get the separation he needed, and his legs did the rest.
Rosen launched a throw to Kirk that traveled 53 yards in the air and resulted in a 75-yard touchdown to put Arizona up one early in the game. The Cardinals would go on to win 28-18 at the San Francisco 49ers for their first victory of the season.
The play was installed Friday. When the idea of taking a shot early was brought up, Rosen loved it.
It was the type of toss Rosen became known for at UCLA and one that showed off his arm, which often was described as NFL-ready leading into April's draft. It was the type of throw the Cardinals were missing from Sam Bradford during the first few weeks of the season.
It also was the type of throw that could spark an offense that is in desperate need of stimulation.
"It shows a lot of the potential of our offense," Rosen said. "We're not really clicking on all cylinders, but I think it shows what happens when we are. I think we can be unbelievably dangerous, especially the way our defense is built and how we've got some unbelievable guys in the secondary, and we've got some real good pass-rushers.
"So, if we can get up in a game and make a team have to throw the ball, I think teams can be in a lot of trouble. We just have to continue to get better and better."
Under Rosen's guidance for the past two games, the offense has been steadily ticking upward. It has produced the two highest scoring games of the season thus far.
And maybe most importantly, Arizona won Sunday.
But there's plenty the Cardinals' offense needs to work on. It's still quite unproductive. It is ranked 30th in points and last in yards and time of possession. Against the Niners, the Cardinals had the ball for 19:49 -- less than one third of the game. Arizona's defense scored one touchdown Sunday, and the turnovers it created led to two other TDs.
Arizona's running game has been stagnant. It has 323 yards through five games this season; 11 NFL players have more yards individually.
But that touchdown pass Sunday could be a preview of what is possible with Rosen at quarterback.
Cardinals coach Steve Wilks said the goal of that pass was just to be aggressive and "stay ahead of the sticks." It showed how the Cardinals could stay ahead of the curve.
"I think we were just trying to get a spark in any way possible and just trying to get the offense rolling," Rosen said. "We haven't been scoring as many points as we wanted to. So, I think we took a really good first step."
The Cardinals could take a while to get to the next step, and possibly the step after that.
Rosen said he's still trying to "break in the offense."
Since he didn't get a lot of first-team reps in training camp, these games are his chance to work out the kinks, on the fly, in living color.
But he's getting there. They're getting there.
"It's a long season," Rosen said. "We've got a long ways to go. Even if we didn't play as well as we wanted to, at least we had more points than the other team."
The Cards have to start somewhere.