Rosen impressed his coach and offensive linemen during the first day of Arizona's first voluntary organized team activities Tuesday while sharing reps with undrafted rookie quarterback Chad Kanoff.
"He was good," right guard Justin Pugh said. "I was surprised at how well he did with the limited amount of time that he's spent here so far.
"The first thing I told him was, 'Take command of the huddle. This is your huddle.' He did a good job. I was impressed with what he did today."
Starting quarterback Sam Bradford was given the day off, and his backup, Mike Glennon, left practice within the first 20 minutes after vomiting on the field. Coach Steve Wilks said Glennon had "a little bug. I think he ate something wrong." Wilks said it wasn't anything serious, and Glennon should be back at practice Wednesday.
That gave Rosen more snaps behind center, and he capitalized on the opportunity.
"Josh looked great today," Wilks said. "Some of his timing and his throws with the quarterback and tight ends I thought were right on point."
Rosen benefited from having veterans around him Tuesday, Wilks said. The speed, tempo and urgency were all greater than during rookie minicamp over the weekend.
"You can see the difference," Wilks said. "I think that was a plus for him, just the operation of getting in and out of the huddle and working with the older guys."
It didn't take long for Rosen to take command of the huddle, a few veteran offensive lineman said.
"He stepped in the huddle and had a lot of pizzazz," left tackle D.J. Humphries said. "He didn't seem like he was choked up at all. Voice didn't crack none. He wasn't talking low. He was excited. He was asserting himself into the huddle, and I was pretty excited to see that."
One of the first things Rosen did in the huddle Tuesday was introduce himself, Pugh said.
"'Hey, what's up, guys? I'm Josh,'" Pugh recalled Rosen saying.
Pugh pointed out that Monday was likely the first day a lot of the veterans met Rosen, so the light-hearted introduction was well received. But Rosen isn't out of place with the veterans. They're all trying to learn the playbook together, Pugh said. Even though the veterans had about a month's head-start on Rosen, Pugh doesn't think Rosen is that far behind.
Neither does Wilks.
"I really don't think it's going to take him long, just for a mere fact that he's extremely smart, very intelligent," Wilks said. "And most importantly, he puts the time and effort in. I think with him working with [quarterbacks coach Byron Leftwich] -- with the rookies, we can keep those guys a little longer, as far as time frame as far as meetings -- I think he's going to be able to pick it up quickly."
Rosen's intelligence was on display throughout practice, Humphries said, starting with the command of the huddle and offense, which he checked in and out of at times.
What impressed Humphries the most Tuesday was when Rosen turned around while still in the huddle to ask a coach a question about a defensive look, which Humphries described as random.
"That, to me, is a big deal," Humphries said. "A guy that's confident enough in himself to understand that, 'Hey, I don't know that. I'm going to turn around and ask this coach that knows. I don't mind pausing all of this stuff so I can figure this out, and I'm going to get out here, and I'm going to snap this ball, and we're going to get it going.'"
Rosen, thus far, has matched the person Humphries saw on TV and texted leading up to this week.
"I was excited to see how much of himself he was. He wasn't trying to force this 'Rah, rah,'" Humphries said. "He was the same way [when we] were texting. He was the same guy that you meet out here and same way he carries himself on TV is the same guy you meet out here. And that's exciting.
"I'm really excited to be around a guy that's confident in himself and is himself. I feel like that's the same way I am. That's exciting to be in the huddle full of guys who are just like that."
Pugh, who signed this offseason as a free agent after five years with the New York Giants, expected the level of calm that Rosen displayed Tuesday because of Rosen's pedigree.
"If you're a good quarterback and you're supposed to be drafted that high, you should come in and have some demeanor about you," Pugh said. "There's a reason why he was projected to go very, very high and he did go high.
"I expect a quarterback to be like that. I'm coming from a place where I had Eli Manning, who was like that ultimate calm, cool, collected. He had some good demeanor about him, and it was impressive."