It just depends on what you buy. Read the label, as it's what the law requires anyway.
Roundups active ingredient is glyphosate and they have added or removed other supplementary ingredients over the years for different reasons. Some are emulsifiers. Others are additional herbicides which may cause quicker "browning" to please the customer
I’m under the impression that the roundup from 15 years ago is completely different than what’s in stores today.