Re: rolled-up sleeves
I do not know of a specific rule of ettiquette outlined anywhere that states whether one should or should not roll his gi sleeve.
Loose clothing is dangerous, including sleeve rolls. Ask anyone who has been caught on a hakama or a shirt sleeve. I prefer students to wear appropriately weighted gi hemmed just above their forearms. Not everyone does it, but it makes training safer so I promote it.
I once heard an instructor tell a poorly dressed student. "If you were going on a date, I bet you'd wear clean clothes that fit well. So why do you come to my class wearing a dirty gi that doesn't fit?"