If the rock is massive, unfractured, and much stronger than the bearing pressure of the footing, there may be no lateral pressure exerted against the wall by the footing (or the weight of the rock). Theoretically, there will be stress against that plane, and it can be estimated using elastic analysis. As a practical matter, the deflection will probably be so small that the wall just won't take notice.
If the rock is highly fractured and the fractures are clean, it can be treated like a dense angular crushed stone. The pressure can be calculated using elastic theory, assuming the wall is relatively rigid, and multiplied by two because the theory assumes the plane deflects as if there is rock on the other side, not your "perfectly rigid" wall. If the wall is flexible, such as a cantilever wall, you can use active pressure theory, which estimates the minimum pressure to hold back the material if the load can follow the wall.
Other cases or very high loads need the advice of an engineering geologist.
My mentor gave me some advice about basement walls. "What ever soil pressure you calculate, don't design a wall that can't hold back water, because you never know when it may need to"
