I'll bite. No, I don't think you can really slow roll someone online.
First off, the "classic slow roll" involves someone turning over their cards, thinking they have the winner. As they reach for the chips, the opponent turns over their cards to show the winner.
In every online room I've been in, you don't have an option of whether to turn your cards over if you've been called and are the winner. (In SOME rooms you can muck or show if you're the LOSER, but the winner is automatically shown by the house.)
The closest you can come (in my mind) to a slow roll online is to use all of your clock before calling if you have the nuts. Do I care if someone does that? Not really. Unlike some people online, I can wait 20-30 seconds to see what they do. That's not that much out of my day to let it worry me.