Finding out about nicknames respectfully

I recently started substitute teaching, and I’m wondering about calling students by nicknames. Specifically, I’m wondering when to ask if a student has a nickname. So far, I usually just ask “do you go by (name on the roll)?” when a kid’s name seems long or unusual, but I’m worried that might be rude to assume they’d go by something else. Any suggestions?
realsocialskills said:
It’s not a good idea to single particular kids out to ask them about nicknames. 
Particularly since doing so is likely to be racist (whether or not you mean it that way). Kids with WASPy names are allowed to use their names, and are able to expect that teachers will pronounce them correctly. Kids whose names aren’t WASPy are often pressured to either go by nicknames or allow teachers to mispronounce their names. It’s easy to end up putting pressure on those kids if you single them out, even if all you 
There are a couple of better options for finding out if there are kids who go by nicknames:
Option #1: Announce at the beginning of roll call that kids should let you know if they go by a nickname, then assume they will tell you. 
Option #2: Ask *every* kid what they go by. Eg:
  • “Alexander Smith?”
  • “Here”
  • “What should I call you?" 
If you do either of these things, sometimes kids who like to mess with substitute teachers might tell you that they go by something ridiculous as a prank. I’m not sure what the best way to handle this is. My guess is that so long as they’re not asking you to call them something insulting, it’s better to just go with it. I don’t think it would do any real harm to spend a day calling a kid Batman; it would do harm to argue with a kid about their actual name. But that’s a guess, and I’d welcome input from folks who actually have dealt with this situation.
Option #3: Look for clues in the environment. If you are in an elementary school classroom, a lot of things will have students’ names on them, and they will probably be the names students actually go by. If there is a behavior chart/wheel (not a good thing, but they’re common), it will have students names on it. Student cubbies (and possibly coat hooks) will be labelled with their names. There might be a shelf of folders with their names. If you can find something like that, it might work to take roll with that in addition to or instead of the official list.
Teachers and especially substitute teachers, what do y'all think? How do you find out about nicknames without singling any kids out?