One of my former sensei taught us that rolled-up sleeves had the same meaning as putting the right side of your uwagi over the left side.
...so don't do it...
I have the feeling that he was right. Not necessary by "the meaning" but that rolled-up sleeves would rarely be a good idea.
As this is a question of etiquette, I would like to ask you to just answer the following questions:
1) Do you know any picture or video of O-Sensei wearing rolled-up sleeves?
2) Do you know any written down rules which deal with the question of rolled-up sleeves? (especially books...)
When I went to ju-jitsu they said they knew immediately that I was an Aikidoka because I rolled my sleeves up.