Brian Flynn took Doncaster from second when Saunders left to join Wolverhampton Wanderers, but Ryan has credited his former boss for several of his signings.
"I must pay tribute to Dean Saunders," Ryan told PA Sport. "He put this team together and made some great signings - such as Rob Jones and David Cotterill who have both been named in the League One team of the year.
"It was difficult circumstances in the summer after relegation but he left us in a great position and his contribution should certainly not be forgotten.
"I must also pay tribute to Brian Flynn who took it on and finished the job. Those two and the whole squad, can be proud of what we have achieved."
Saunders's current club Wolves are struggling to avoid relegation.