Older cat urinating in house because of new cats in household

Question
I moved in with a roommate who has a 16 year-old, female, spayed cat (Ruby) who lost her litter mate about 4 years ago and who seems very lonely.  I have two litter mate females, age, 5 who are spayed.

We slowly allowed the cats to interact...my cats have their own food area and litter box.  But one of my cats (Jill) has started to move into Ruby's territory.  She sits on Ruby's cat furniture, uses her litter box and sometimes nibbles her food.  I try to shoo her away as much as possible.  

Now Ruby has started to pee in my roommate's room refusing to use her litter box.  She is not spraying he is urinating heavily in boxes, on carpet...anywhere but the box.

I got Feliway plug ins and am trying to keep my cats locked up now...hoping Ruby will go back to the cat box (I bought a new one so the smell of my cats wont be on it).

How can I get the older cat to feel okay about sharing the house.  I have been here two months and this only started a couple days ago.

Thanks!

Answer
I hate to tell you this, but locking your cats up now will only make your cats more angry about this situation. It could make Ruby happier, though. And obviously Ruby is displaying her frustration with urinating in your rommate's room. I also wouldn't have shooed Jill away. The ultimate goal is make them all welcome to live together and this just says, "no you have to live separate." Did Ruby act out at all with Jill doing this? At what point did Ruby start doing this? Was she fine until Jill started invading in her things? Was there ever any fighting going on?

I would honestly try another introduction, but use food as a mediator and have a dish for each cat. Ruby needs to be reassured that your cats are not there to pose a threat.