We have a retaining wall going not quite the width of the back yard. Our neighborhood is situated on a gently sloping hillside with most individual lots leveled off. The back neighbor's yard is all at a higher elevation that ends with a planting bed on our side and a retaining wall. The wall used to be three rows of simply stacked cinder blocks. Not a good solution at all, but the previous owners were not concerned with the look of their yard:-). We finally had the blocks removed and rebar put into a cement foundation.
The entire planting bed consists mostly of tree roots with some soil in between:-). My roses still grow and bloom there (but not at the time the wall was done in early March), even though I hear again and again how bad tree roots are for roses (and no doubt for lots of other things, including walls and sidewalks).
The blocks were then put back...
... and topped with stone tile.