Partitioning your SSDs to make a root partition for controller B is not useful - it does not improve performance of the system, as the root aggregate and root volume is only used for booting the system. I recommend to leave it as is - SAS partitions booting each controller, then have a SSD data aggregate on controller B. Can you help me understand what you are trying to acheive?
Can you post the output of these two commands to assist further:
storage disk show -partition-ownership
storage pool show
storage pool show-disks