Rovanperä was two seconds faster than anybody on his opening run at the 3.79km Olmedo test, before coming undone after the flying finish.
The 20-year-old said: “The run was actually good, the feeling in the car was good and, for sure, the time was good also. But then I made the mistake after the finish line.
“Actually it was a bit wrong in my notes and I would need to start to brake a bit earlier than I did. We went a bit wide, but it looks like the car is OK. We had a soft roll but hopefully everything is fine for the rally.”
Toyota Gazoo Racing has subsequently confirmed the Yaris will be repaired overnight and ready for the opening stage.
Video: Rally Italia Sardegna shakedown
A team spokesperson said: “The damage was light, it wasn’t so bad – we are confident for tomorrow.”
Rovanperä added: “I’m looking forward to it. The pre-event test was good, we made some changes and I think they worked.”
Like many of his fellow competitors, he believes the opening 12.08km Tempio Pausania speed test will be a big challenge.
“It’s a new stage, quite interesting and it looks like it has been just made. It’s going to be quite soft, so in stage one, the second loop will be I think quite demanding. It’s really tricky stage, quite narrow and slow and it’s going to be quite soft,” he explained.
• Full coverage from Rally Italia Sardegna will be available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.