802.3ad and LACP are not (yet?) supported in hardware on CRS switches - and doing it in software maxes out your CPU and performs poorly to put it in a polite way.
You can try a static bonding following
this Wiki Page.
Additionally, bonding on ESXi is only supported with distributed vSwitches which is part of the enterprise plus license.
But you can achieve a similar solution by adding a rOS vm to your ESXi host, add a NIC per physical NIC to it and create a vSwitch per physical interface, enable promiscous mode. Do not connect any other vms than the rOS vm to those vSwitches.
Now in your rOS vm set up a bonding interface over all vNICs.
For the vm network(s), create a new vSwitch without any physical interface and hook up the rOS vm to it as well as all vms.
In your rOS vm, create a bridge and add the bonding interface and the vm-vSwitch-facing interface to it.
That works.
-Chris