*Do not do this* with write access repositories, is my advice from knowledge of NFS filesystems. Writes, and partial writes, can occur from one host for the next "commit" but not actually be seen on the next "round robin" server until a fairly arbitrary amount of time later, due to propagation delays inherent in NFS. There's a lot tht NFS can do well, but this is not one of those tasks.
I'd really encourage you, for commercial graide high availability or load distribution, to look at WanDisco's "Multi-Site" or to use a failover load balancer setup. If server 1 goes toes up, serer 2 is available, and handles all the traffic. But mixing and matching back and forth randomly as can happen with round-robin? That sounds like a dangerous idea likely to bite you at really, really bad moments due to simultaneous commits through two different NFS enabled front ends.