Depends on the roe, I think.
For humans, turds and penises often have some overlap in size, meaning in order to fit a turd out the poop chute, it has to be able to fit something roughly that sized. as it so happens, that size and shape is similar to the penis.
For fish, they push out little tiny eggs. Which means their fish-ginas are sized proportionally to what they were built to push out. If a fish, human sized or otherwise were to push out big round roe the same diameter as a penis, then it would stand to reason the fish-gina in question would be able to take something that large in.
Of course, roe and eggs aren't always proportional to the size of their adult species.