What do we know about Rosa's past? Why does she think hitting her children with wooden spoons is acceptable?

Rosa's past is speculation because we know nothing about her it. Judging from her present we might consider that love was not externally expressed in her childhood. Max, for whatever reason, comes on the scene and we see her as beautiful for the first time through her care of him. Maybe she lost her dad as a young girl, and maybe that's what made her own life so difficult. In the end, she becomes an endearing figure all around.