I use Mikrotik routers on our network in order to be able to do bandwidth tests (BTest).
If I connect the Mikrotik on a Netonix, the switch pass the port in “forwarding root” and the Mikrotik becomes Root Bridge ID…
To disable the root bridge I did the following action on the Mikrotik : Bridge > Ports select “Interface > all”
Bridge Port and selected yes on Edge selector.
“root bridge” is a feature of xSTP. If RB in question can not create any loops (e.g. it only has one connection to the rest of network), then you can disable xSTP entirely:
/interface bridge
set [ find protocol-mode!=none ] protocol-mode=none