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My best guess would be he didn't like her choices and was fed up. I think he might have also intended on only hurting them or maybe a conversation escalated into a crime of passion. My best guess is that there was two confrontations. I don't know exactly when the first took place, but the first would have been her brother confront her and/or Roger about the fact that they were together. He's married. He's ten years older. Her last boyfriend was violent. She had a daughter at home and he and his wife had wanted kids but couldn't have them. There may have been more, but I think that was the core of his problem with her. I think in the first confrontation, Roger may have gotten him heated. I think Rose may have also played a part and threatened to tell things she knew about her brother--things along the lines of sexual abuse. Maybe Roger thought he was being protective of her by keeping her away from the brother.
If the brother was truly the killer, something caused him to go out of his way to see her that night. Something had to be dealt with. That said, I still believe the killer carved the soap. I can't help but think it was just something being done while talking/listening, or waiting after it was done.
Here's a theory I had quite some time ago, while I still believed it was the brothers, but could apply here too. Maybe Roger was killed and Rose locked herself in the bathroom. Maybe she wrote the message on the mirror and maybe it led to the killer, which the killer then later wiped out after coaxing her out. If it was the brother, the message on the mirror makes little to no sense. The only thing that would make sense to me is if he was trying to be misleading and changed his mind. Maybe he was trying to point it in the direction of the ex or someone else.
In answer to your other questions. I have no idea if the brother was ever a suspect. My guess is no, because there was already a rich list of suspects. I know the focus was on CRH for a little while. I know they thought the ex boyfriend seemed obvious until his alibi checked out. The bartender thing was suspicious. I bet the brother didn't seem like a good suspect, mainly because he didn't have a record, a known motive, and they had their hands full with a better more obvious list of people.
One discouraging fact about all cold cases, take Zodiac for example, is that there is often a handful of suspects and a pretty good debate over why I think it's person A and you think it's person B, and they think it's person C, but in the back of my head, I always wonder if the killer isn't even on the list. In this case, it may be possible. All the theories and guesswork are useless because the actual killer wasn't even suspected or mentioned.
I don't know what the relationship between half-brother and professor was. The man I spoke to thought it was interesting that he only said something shortly after half-brother died, as if he was protective, or even scared of him.
The man I spoke with also believed it was Rose's mother babysitting that weekend. He said she had been with Rose in the days leading up as well and knew where Rose was going. Rose called the babysitter according to articles at the time, so that means she called her own mother and told her where she was. Did her mother support what she was doing? It seems possible at this point. Would the mother have seen any harm in her own son knowing? Probably not. But then the question is when law enforcement questioned her on whether or not she told anyone else where they'd be, what did she say? Did she tell them she told her son? It seems to me that would have made him worthwhile of a look.
I know the men on Roger's crew also knew where he was going and there's been some implied issues between some of the crew and Roger, because of his infidelities. Maybe he'd gotten with one of their girls at some point. Still...how would they know the hotel? How would they figure out the hotel number? Goes back to the brothers possibilities we'd discussed.
I think part of this might be about Rose's daughter. I think someone, or some people, didn't like how she was raised. Half-brother probably acted alone but I'd guess the family would have figured it out, accepted it, protected it.
But this is all just guessing at this point. If the half-brother thing is true, DNA is really all that's left, other than someone to come forward from the family. Even then, how and why probably died with him.
