Rosewell was speaking at an event held by the Ministry of Housing, Communities and Local Government to mark the one-year anniversary of her landmark review of inquiry appeals, which included 22 recommendations for reform.
PINS has so far implemented 16 of Rosewell’s recommendations. Figures published this week show the average timescale for inquiry appeals is now 24 weeks, down from 47 weeks before the Rosewell review.
"I wasn’t sure I really believed it would go as well as that or as fast as that," said Rosewell.
She added: "One of the things I said to people while we were doing this is, don’t be surprised if you have a few more judicial reviews than you did in the past.
"One of the ways the system decayed was because people were falling over backwards to accommodate every single possible way that something could be challenged and that just resulted in putting more time into the process.
"It may well be that you’ll lose a couple of judicial reviews. Frankly, I think that’s ok.
"We shouldn’t be scared if that actually happens. Hopefully it won’t. But if it does I’d see that as teething troubles rather than there’s something actually wrong in what we’re trying to do."
Recommendations still to be implemented from the Rosewell Review include the launch of a digital portal for submission of appeals.
Rosewell said: "Obviously there are still challenges. It would be astonishing if there weren’t. We’re moving forward on the technology."
The portal would allow the uploading of all inquiry documents and would update all parties throughout the process.
PINS had set a date of June this year for its launch but a spokesman said: "The exact date for the new portal is still to be confirmed but a launch this summer is still expected."
Speaking to Planning, PINS head of operations Simone Wilding said: "When we finally got our portal up and running, that will make another big difference.
"So far that is one of the areas where we ourselves had been hoping to be much further on and unfortunately it has been taking a lot longer than we’d hoped for."
Wilding said the inspectorate was keen to explore other technological opportunities such as live streaming of inquiries.
"Ideally, virtual events, in the longer term that’s where we would want to get but the technology will take us quite a while to sort out," she said.
A feature examining how inquiry participants are adapting to the new post-Rosewell Review rules can be found here.