The first thing that jumped into my head, "She's named for Rosh Hashanah?". (If you don't know, that is the Jewish holy day of the new year and the name literally means 'head of the year' or 'first of the year'. The word rosh usually being translated as the word 'head'. You could check out this site for general info: http://www.jewfaq.org/holiday2.htm
) I guess it isn't a bad thing to be named for, but definately unusual and definately some miscommunication was going on if that is the case.
Also, maybe it could be a variation or combination name of the Jewish name Shoshana
. You can check out this link to the archives for more about this name: http://www.behindthename.com/wwwboardarc/messages/26744.html