Dragons head west to the Parc y Scarlets to face Wayne Pivac’s men on Saturday (kick-off 5.15pm) buoyed by the 23-22 win over Ospreys at Rodney Parade.
And Rosser – a try scorer in the home win – believes Dragons can make the trip with optimism as they look to replicate the form of the last two derby games.
“It’s a massive test ahead,” he said. “We were on the wrong end of the scoreboard last season so we know how much of a task it is going to be, but we can take a lot of confidence from the Ospreys game.
“We’re in a better place as a team than last season, we are tight as a group and all on the same page in terms of defence.
“We’re away from home and they are coming off a defeat so they will be fired up for it. We know how hard it is going to be.
“Derby games are like no other. You’ve got to bring belief and aggression.”
Rosser was delighted with the win over Ospreys – but admits he feared a repeat of the late loss at Cardiff Blues when the visitors had a late penalty attempt.
“It was a nervous finish with it all coming down to the penalty. We had a bit of luck there,” said Rosser, who celebrated his 21st birthday on New Year's Eve.
“We’ve been in that situation a few times when it hasn’t gone our way so it was nice to get some.
“We had belief throughout the game and took that into the final 10 or 15 minutes.
“It was the luck of the bounce with my try, but I was just happy to get it,” he added. “Quite often the not so scripted kicks are the ones that work out and cause damage. It’s important to chase every kick.
“We know how much this win means to the fans. We could hear them into the final few minutes, they really got behind us and helped us lots as a team.
“It’s a massive win. It’s been a tough couple of weeks back at Ystrad Mynach, but we knew we had to stick together and go into every game as one.
“We knew that these games over the derby period were important and knew that if we performed well it would carry us through for the rest of the season.”