It's main purpose is to serve as deterrence - a "dead hand" solution, that could be pre-launched during period of high tensions as a warning. The opponent planning a first strike would be forced to dealt not only with the possibility of pre-launched missiles getting attack order, but aslo with the possibility of them not getting cancel order. It makes decapitation strikes far less attractive; what the point of destroying enemy leadership, if pre-launched missiles would still get you, because you destroyed the ones that could told them not to?
This places a lot of faith in communications links, given it is an unmanned platform. I highly doubt it would be launched ahead of time, or if it did, I simply do not believe striking its target would be its default setting. And this scenario seems to assume the rest of the Russian deterrent is somehow vulnerable, which seems highly unlikely.