I don't think the light flicker has anything to do with rolling shutter, as most of the DSLR's if not all the ones we use will have rolling shutter. You'll find the more expensive ones (up the 8k mark like the RED, ARRI, PANAVISION & BMUMP) will have global shutter.
I think what you're referring to, and please correct me if I'm wrong is the shutter speed. Now depending on what lights you have (whether they're 50Hz or 60Hz) it's a simple fix of changing your shutter speed to 1/50 or 1/60. Because these are frames only, you can in theory go up to any amount as long as the shutter is in tack to the lights hertz.
Now I don't remember if C920 has shutter speed selection. If not, make sure anti-flicker is turned off in the pic above it doesn't look like the case. And just adjust the exposure accordingly. If you have another light that'd be preferable. Or even something to just bounce the light to, like something silver / reflective or white foam.
It's really a trial and error bud, I wish you well.
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