I don't believe we have a specific version or matrix for the last version of SANtricity OS that was compatible with OpenStack Rocky.
The OpenStack Rocky matrix lists out the various functions that are supported on E-Series platform. The matrix was updated in October 2020 which was around the time of the latest SANtricity OS release (November).
I received some feedback from our E-Series engineering team. The last fully tested E-Series software with Openstack is 11.50.x.
There aren't currently any plans to test newer version of E-Series software with OpenStack.
If you are looking for further guidance on this solution and potential software upgrades, I suggest you reach out to your NetApp account representative. They may be able offer some product variance certification for your specific environment and use case.