Mercedes comfortably topped the mileage charts in the opening test at Jerez last month, and has continued to cover plenty of distance at Sakhir - but caused two early red flags on Thursday.
Rosberg still managed 85 laps during the day, and said doing that much running also meant more problems would be found.
"It's the result of doing many laps," he told AUTOSPORT.
"When you start to do that many laps, naturally you'll start to see the problems in the car."
Bahrain day two report
The German acknowledged that returning to the pits on a truck was never ideal, but did not see Mercedes' more public troubles in test two as a problem.
"Issues are issues - if you stop on track, it's never good," sad Rosberg.
"Although it's important to do it now to see what the problems are, because for sure there are going to be problems on the car, none of them is perfect.
"So we need to push this car to the limit, get to the problems and see them, then fix them for the races. Stopping on track isn't necessarily a bad thing."
Bahrain F1 test photo gallery
He said Mercedes had been able to begin concerted set-up work on day two in Bahrain.
"We've started working on the set-up, and today, from that point of view, was a good day for me, because I felt at home and comfortable in the car and was able to attack and that was a nice feeling," said Rosberg.
AUTOSPORT Live coverage of Bahrain testing will resume from 6am UK time on Friday