Ken,
I just found a workaround to prevent non admin users to add / edit
/ delete announcements,
Edit AccessPermissions.xml found under \ManageEngine\ServiceDesk\server\default\conf
Append the following lines as in the screen shot below,
<url roles="SDAdmin" path="/Announce.do">
<param name="mode" type="String" regex="addnew|delete|edit"/>
</url>
and do a application restart.
The buttons will be still shown, however clicking on it will show up a message that they do not have permission.
Jai Anand K
ServiceDesk Plus