Saunders left Doncaster on Monday after almost 16 months in charge to take over at Wolves, who sacked Stale Solbakken on following their FA Cup third-round defeat at non-league Luton.
Interest in replacing the Welshman at the Keepmoat Stadium has been high, with Ryan impressed by the calibre of applicant the south Yorkshire club are attracting.
And Ryan is confident he will be able to find the man with the right attributes to carry on the work done by Saunders, who leaves Doncaster joint-top of League One.
"Dean's achievements here have been incredible when you look at the situation when he arrived and where we are now," Ryan said. "Given our position, it's not the best timing. But it never is and that's football.
"Whoever we pick, we'll probably get criticised. When we appointed Sean (O'Driscoll) and when we brought in Dean there were people questioning it, but now look where we are. I think our judgement has been pretty good.
"But in my 15 years at the club we have always had a plan B and we won't be distracted from the big prize (of promotion).
"Getting back in the Championship is the over-riding ambition, that's the aim for the rest of the season. We've got as great set of fans here and a great set-up with the Keepmoat Stadium and the training ground - everything is in place.
"I'm sure we'll find someone who we think is capable of taking us there. We've already had a lot of applicants, and a lot of very high-quality applicants."
Former Wales Under-21 boss Brian Flynn, who has been working for Doncaster as a scout, and captain Rob Jones have been placed in temporary charge while Rovers conduct their search for a new manager. The club hope to make an appointment in time for their League One fixture at home to Leyton Orient on January 19.