Tame rat and housemouse together

Question
My name is Oscar Rat and I'm a famous fiction writer.  Being a virtual rat, I talked my human companion, Charlie, into taking in three tame males.  One, Sasa, loves to run around on the floor.  He's let out every morning for an hour or so, and comes when called.  

I also have a wild housemouse named Jeff.  He also considers the floor as his own property.  At first, Charlie tried humane traps to catch Jeff.  One time, he even caught him in the rat cage, eating from their bowl.  He was groggy and Charlie grabbed him by hand.  Then, Jeff was taken out in the cornfield and left loose, with a large chunk of chocolate to tide him over until he could find gainful employment.

That night, Jeff was back, and angry.  He's not as trusting as before.  I told Charlie to feed him, so Jeff gets fed well, in his own food and water bowls in a bedroom.  

Jeff has been around for almost two years now, and is very large for a mouse.  After one accident, he leaves electric cords alone.  After biting into one, he ate only cookie soaked in milk for a couple of weeks.

Well, my one rat, Sasa, found he could jump off the couch and loves to run on the floor.

Recently, he and Jeff have met--several times.  They seem friendly, so far.  Jeff is about half Sasa's size.  In a fight, I don't know which I would bet on.  Sasa is a gentle rat, never starting fights among his fellows, and never biting Charlie.  Jeff is very fast, and Sasa seems fat and slow.  They are both very well-fed, so hunger wouldn't be an issue.

My question is, is it safe for both of them on the floor together?  

Oscar Rat, the famous rodent fiction writer.  (Google for my work.)

Answer
Rats participate in a behavior known as muricide -- that is, they routinely find and kill mice in a wild setting. Personally, I wouldn't be comfortable letting two animals I cared about run around on the floor together. Also; given that Jeff is in fact a wild mouse, he is more prone to carrying certain diseases, notably Sendai and SDA virus. Both are really nasty critters and can lead to the death of domestic rats. Please, by all means, google Muricide and Sendai/SDA Virus for a better idea -- after that, it's truly your decision.

Thanks for writing :)