Some rock formations in the path of a glacier are sculpted into small hills called roche moutonnée, or "sheepback" rock. Roche moutonnée are elongated, rounded, and asymmetrical bedrock knobs that can be produced by glacier erosion. They range in length from less than a meter to several hundred meters long. Roche moutonnée have a gentle slope on their up-glacier sides and a steep to vertical face on their down-glacier sides. The glacier abrades the smooth slope on the upstream side as it flows along, but tears loose and carries away rock from the downstream side via plucking.
How large are roche moutonnee?
less than a meter to several hundred meters long
The given context describes roche moutonnee as small hills that are sculpted by glacier erosion. It also mentions the range of sizes for these rock formations, from less than a meter to several hundred meters long.
Based on this information, it is clear that "less than a meter to several hundred meters long" is an appropriate answer to the question: How large are roche moutonnees?.