It is possible to register more than 1 vCenter to same vRO server (my goal is to use context actions from many vCenters, from single vRO).
my vRO authenticator configured to use with vCenter (and i only can use context action from this vCenter)
Yes, it is possible. However, as vRO can use only a single vCente/PSC endpoint as authentication provider, in order to be able to use vRO context actions in your multiple vCenters, they must be configured in such a way that each of the vCenters can validate other vCenters' SAML tokens.
See the following recent thread in vCenter community forum where the same use case is discussed - https://communities.vmware.com/thread/604784