Yes, you can go to Configure > Certificate > Advanced Options > Import Ruckus PKI Certificate Package, enter the number of APs who need new certs, and click the "click here" link. (It's kind of hard to see, but it's there.)
This will create a .req file, that can be sent to Ruckus using
https://certrenewal.ruckuswireless.com, and Ruckus will send you another file, that can be used (in the same section in the ZD UI) to import new certs for older APs.
Instructions are also in the ZD 9.13 User Guide, and the Online Help. But this is a short version. Hope it helps!