Renaming "add new announcement" in a sharepoint list

I work for a law enforcement agency and trying customize the sharepoint to fit our needs and here is the problem..

I have created an announcement list in sharepoint and added a webpart on my homepage to display this list.

At the bottom of the webpart you have the option to "Add new announcement". Does anyone know how to rename "Add new announcement" to "Add Roll Call Item" ??

Appreciate any help...