No it is not common in yorkies but can happen and genetics is believed to play a role.
I have never heard of a yorkie suffering in pain from a roach back ,it should not interfere with her comfort or life span.
Only problem would be breeding or in showing she does not conform to standard.
We look forward to seeing pics of your much loved yorkies
description of body type from akc.org
Body
Well proportioned and very compact. The back is rather short, the back line level, with height at shoulder the same as at the rump.