So in my 'New Guest' comic, there was a page where Robotnik revealed a bit of information she shouldn't have known.
When Chuck asks, Robotnik says that Bunnie Rabbot told him and hints that she was tortured.
So I drew Robotnik having his way at getting Bunnie to talk.

Comic Page - Part 8 - Page 17 - http://whoknows4682.deviantart.com/art/New-Guest-Part-8-Page-17-566192683

I would imagine that Robotnik would see himself being above doing something like this (a waste of time for him to personally do it), and would usually get his robots to do the torturing instead of himself.
Though with the group of Freedom Fighters that have given him the most trouble out of all the small pockets of resistance, I can see Robotnik taking time to deal with them himself.