Word definitions
rovedzera: become quite accustomed
mawere: steep rock face, especially a tall one
Translation
What one has become accustomed to takes root; a baboon climbed a steep rock face in the dark.
Inspiration for proverb
Baboons are excellent rock climbers, and can even climb up very steep rock faces.
Application
What one has become so used to, they could still accomplish even under the most challenging circumstances.