Ros support is enabled by default, but it can be turned off by disabling the following options:

• ENABLE_yarpcar_tcpros_carrier (the usual protocol for topics)
• ENABLE_yarpcar_rossrv_carrier (tcpros with minor tweaks for services)
• ENABLE_yarpcar_xmlrpc_carrier (used by ros nameserver and node interfaces)

YARP does not link to any parts of the ROS codebase, so don't worry about how to tell YARP where to find the ROS libraries, it doesn't need them. You do not need to have ROS installed in order to interoperate with it across the network.