Training a cat... Calling all owners and experts.?

Sorry, but at age 18 the old gal probably isn't changing a thing. It is possible to train cats, but it's difficult and pretty much impossible by the time they reach the age of your roommate's cat. The only options you really have are to crate her or isolate her to a single room so she can't scratch on your door. Of course, if she's not happy with being isolated she may still make her presence known by meowing. I wish I could offer you more advice, but I really don't foresee that the cat will change. Maybe if you talk to your roommate, s/he would be willing to get up a little earlier to make sure the cat is taken care of to hopefully avoid the issue.