Well, you only care about what actions to do and what order.
If your edges are 'building things' and your nodes are records of some type (current time, number of stuff, stuff currently building), then you can calculate when you will be able to build what next, and generate the descendent states.
Given we are interested in four types of buildings and three types of units, that's maximum 7 descendents per node. Getting to 7 roaches doesn't require more than 20-30 actions. That's 7^30 and too much, but a lot of states are easy to prune, e.g. don't build 2 zergling dens, and on top of that you can add some goal searching heuristics, like a*.
If your edges are 'building things' and your nodes are records of some type (current time, number of stuff, stuff currently building), then you can calculate when you will be able to build what next, and generate the descendent states.
Given we are interested in four types of buildings and three types of units, that's maximum 7 descendents per node. Getting to 7 roaches doesn't require more than 20-30 actions. That's 7^30 and too much, but a lot of states are easy to prune, e.g. don't build 2 zergling dens, and on top of that you can add some goal searching heuristics, like a*.