I am not sure who defined slow roll for you all but it can not happen online, its not possible. A slow roll is where you have ALREADY called the bet and wait to turn your hand over - has NOTHING to do with calling with the nuts...its a live action play only, and is very very rude - may even get you into a fight, I do not recommend it.
Taking your time calling anything online can mean anything - slow internet, slow computer, multi-tabling, not paying attention - if you read anything into it you will have issues in the future for sure.