Is sulfuric acid still hazardous after it dries?
Sulphuric acid won’t dry — meaning evaporate; what water does when one typically thinks of drying — at any noticeable rate. It will, however, given time penetrate deeper into the material if the material is porous or susceptible to degradation.

Depending on how much sulphuric acid was actually spilt, I suggest either mopping up the area with lots of water (if not much was spilt) or first semi-generously applying dry baking soda to the area. Once the baking soda has stopped generating bubbles immediately on application, you can use normal amounts of water for wiping up.

While I would love to suggest you get the sloppy housemate to do it, I think you might be disinclined because they again will do it sloppily.