Unified Workspace does not currently work with Remote Desktop Connection Broker.

Here is a URL on how a Remote Desktop Connection Broker works:

The reason that Unified Workspace does not currently work is that when you are told to connect to a different RDS server we are unable to do that because the connection tunnel to the RDS server has already been established. 

The way the Remote Desktop Connection Broker works is that your RDS servers are part of a DNS round-robin DNS name. A user connects to a "random" terminal server. The RDS server asks the Remote Desktop Connection Broker if it should take the user's connection or pass it on to another RDS server. It is the passing on to another RDS server that is the problem.

The RDS server sends a redirect/reconnect RDP packet to the client telling them to disconnect and re connect to a different IP address. Because Unified Workspace sets up a 1-1 tunnel between the user and the initial RDS server when the tile/link is clicked, it can't detect that the user was told to go to a different RDS server.

Depending on how you have your RDS servers configured with the Use IP address redirection option, you may be able to just add all of your RDS server IP addresses to the host object in Unified Workspace and let Unified Workspace handle the "brokering"/balancing of the connections to the RDS servers.