Google Merchant is the way a company can feed their products into Google Shopping and ROME is a Java Library to create and parse RSS and ATOM feeds. Google Merchant allows RSS as one of the feed formats you can use to feed them their data. In order to get additional information into ROME created feeds you have to implement 4 classes, so it is not really easy to get your data there.

I created a small Library to make RSS feeds that conform to Google Merchants requirements:

        final SyndFeed feed = new SyndFeedImpl();
        feed.getModules().add( new GoogleMerchantModuleImpl() );

        final SyndEntry entry = new SyndEntryImpl();

        entry.setTitle( "Title" );

        final GoogleMerchantModule merchantData = new GoogleMerchantModuleImpl();
        merchantData.setImageLink( "SOME IMAGE URL" );

        entry.getModules().add( merchantData );

It’s under MIT License up in Github, you can direct download the Version 0.1 here.