I absolutely wouldn’t invite an employee to be a roommate and certainly wouldn’t do so thinking “there would be more to it”.

I also would refrain from flirty texts.

I especially would refrain from doing so if she is in fact your employee not just a coworker. If you are a person who is setting up her salart then she is your subordinate. Being in such relationship with subordinate falls into abuse of power and potentially sexual harassment.

So my answer is a definite NO