Slang for porn or a porno, cause in Roman Numerals, 30 is said as XXX which usually refers to porn.
I'd love to make a Roman 30 with you!
Let's watch some Roman 30 together!
30 Romans is 30 in Roman numerals, which is XXX which is porn
Me: what are you doing?
My friend: I’m jacking off to a 30 Romans video