Responses
I don't think that circle was drawn to bring Hughes back. He said he drew it during the war. The war happened when Winry was a little girl, because her parents were killed then. It was YEARS before Hughes dies, so he'd have no reason to try to bring him back to life. Not sure who Roy wanted to bring back, it implies Hughes, but chronologically, there's just no way.
SPOILER
In the manga he wanted to bring back Winry's parents to life.
you gonna make me cry
I think Roy favourites that room, because that's where he and Hughes used to secretly slept together (as to why Roy mentally states 'she'd never forgive me' towards Gracia).
When he found that Edward was living there, it was pure coincidence. Roy was there because he had been there before with Hughes after they returned from the war, and the chalk was indicator that he was drawing a transumation circle.
Now this takes place /after/ Hughes dies, the circle was meant to bring Hughes back to life.
Edward realizes this and gets angry, since Roy knows what it would've son to him.
So Edward, realizing he was a rebound, decided to drop their 'relationship'.