Can a rock be placed like trees?

Hi, im almost new on this, and sorry if my question is too stupid, but, is there a way to place rocks in places, like the “place tree” tool does? Is annoying to put rock by rock in all places, (i tried putting the rocks on the place tree tool, but rocks seems to be too big)
Also, any tool or something, to put random rocks? I mean, i have 4 rock models, and i want to put them randomly, is that possible too?

The Terrain Details tool might be what you’re looking for: http://docs.unity3d.com/Documentation/Components/terrain-DetailMeshes.html