You do not report the funds received from your roommate on a tax return. You are roommates sharing expenses so nothing is reported on a tax return.
Why doesn't the roommate simply pay the rent directly to the landlord? This will keep this new potential 1099-K situation from happening. Or give you a check or cash ?
Why is the roommate paying you? They have no legal obligation to do so. Their legal obligation is to the landlord, same as you. Have them pay it directly to the landlord.
You can expect to receive some kind of tax reporting document from Venmo. It can be dealt with. But how it's dealt with will depend on what kind of document Venmo sends you. I would expect a 1099 of some type, be it a 1099-MISC, 1099-NEC or 1099-K.