I'm not familiar with Angular, so this may be the incorrect way to do this, but this seems to work on your fiddle ...
change the row to
<tr ng-class="rollClass" ng-repeat="roll in sushi | orderBy:sortType:sortReverse | filter:searchFish" ng-mouseenter="rollClass = 'highlight'" ng-mouseleave="rollClass = ''">
and add the css class
.highlight {
background-color: gray;
}
The idea comes from this SO question