Rossi claimed his first ever dry podium for Ducati in the San Marino Grand Prix, having been given a new chassis and swingarm for the event.
The Italian was further enthused by a new swingarm delivered in the test, while Hayden got his first taste of the new chassis and swingarm Rossi used at Misano.
The American had been unable to race the updates having pre-race testing due to the injuries he suffered in his heavy Indianapolis crash.
Hayden said the updates surpassed his expectations.
"In order not to stress my hand too much, we only did two runs — one with basically my race bike, and one with the new frame," Hayden said.
"I wasn't sure if I would even be able to notice the difference, but I could actually feel more than I expected.
"I felt better with it, for sure. I had more confidence because there's better front grip for braking into the corners, and because of that, also better turning.
"I think it's certainly a step in the right direction, straight away, and I'm happy with the work Ducati has done.
"Because I was able to brake a bit differently, I'll probably need to stiffen the fork spring a bit, but already, it was a good step. I'm quite happy, and at Aragon we'll start to work on the set-up."
Rossi was so encouraged by a new swingarm that he planned to race it at Aragon next weekend.
"It was a good day," he said. "We tried a different chassis that had a different stiffness, but honestly, I didn't like it a lot. It was an improvement in some areas, but we had some new problems in other areas, so I don't think we'll use it again.
"But the positive thing is that we tried a new swingarm that I liked a lot because it gave me more edge grip and more rear grip under acceleration, and it helps the bike to stay more stable on corner exits.
"So of the two things, one worked. I think we'll use the new swingarm starting in Aragon, so there we'll see what our potential is on another track."
Technical director Filippo Preziosi said the test day, and feedback from the riders, had helped expedite production of a new chassis, which could arrive before the Valencia season finale.
"It was a very useful test: Valentino gave us feedback that will allow us to design an evolution that has the positive characteristics that he noticed, [while] Nicky's initial comments were positive," he explained.
"Based on the data we gathered today, we're speeding up production of the next step of the frame, which could arrive before Valencia."
Andrea Iannone, who will step up to Ducati's new satellite squad next season, had been scheduled to also take part in the morning but ended up sitting out in favour of development rider Franco Battaini.