There's not much he can do with the comatose Rosa. Let's explore the place while we wait for her to wake up.
Going through the door brings you to a simple intersection. You can go right to hospital reception, across the hall to an empty padded cell, or left to a doctor's office and a storeroom. Try them all.
In the reception area, the only interesting thing is the window, which shows a rip in the sky that seems to be Madeline's work.
In the doctor's office, you'll find Dr. Quentin from the first game dictating his report on Rosa's condition. Alas! but not helpful.
In the storeroom, there's a notice on the wall to the right of the white lockers that's interesting.
Finally, go into the empty padded cell to find --
-- that it's not so empty after all. If you read the notice in the storeroom, you'll have a long conversation with this guy that explains everything --
-- and nothing. Forget the details; the important info is that Madeline is trying to destroy herself by ... destroying the rest of the city? Well, whatever.
There's nothing else Joey can do on his own. The only thing he can do is try talking to Rosa's unconscious body again. It might work this time; and besides, as he says, talking is all he's good for.
This automatically switches you back to Rosa in the void. Time to go, girl.
How do I get Rosa out of the void?