You can sort of do what you want. There are 2 tags in the template that provide the ratings feature, [RATINGS] which displays the graphical representation of the item's rating, and [RATINGSFORM] which is the actual form that allows a person to rate an item.
The graphics that display the current rating for an item is configurable in the module settings. The images to be used are stored in the /DesktopModules/Repository/images/ratings folder. You can create a new set of images by creating a new folder there, for example a folder named 'noimages'. Then you need a separate image for each rating value from 0 to 10. So create an image that is a button or text that simply says, 'Click to Rate this item'. It must be named the same as the folder + a number from 0 to 10. So you would save your image as noimage0.gif. Then copy it 10 times, renaming each one to noimage1.gif, noimage2.gif, etc.
Then go into the module settings for your Repository and the 'Ratings images' to your new 'noimages' set.
Now, users will not see the ratingm just the image that you created that says 'Click to Rate this item'. When they click on it, the ratings form will be displayed.
Now, here's the sort of I was talking about .. since you can only have one settings for ratings images, Administrators will also not see the ratings value for items. You'd have to devise another way for Admins to see item ratings. One option, if the Admin has host access is to log in as host and run a Host->SQL Query such as 'select FileName, RatingsAverage from grmRepositoryObjects'.. The other option is to put a dashboard on the page and set it so that only Admins can see the dashboard and set the dashboard mode to 'Highest Rated' and the # of items to display to something large enough to display your items. You can place the dashboard on an Admin only page so that it won't affect the load performance of your Repository page.
Anyways, that would be my recommendation using the current build on how to achieve your goal.