It's definitely been considered rude in most of my (USian) gaming circles to touch/roll someone's personal dice without permission. However, lending dice or having a bunch of communal dice available have both been totally normal as well. But if someone brought their own dice and has them sitting in front of them, the assumption would be that you shouldn't play with them without asking.
A lot of people around here also get incredibly superstitious about luck in their dice, and have all sorts of rituals around them. I've definitely encountered people who've gotten upset that someone rolled their die and let the luck out which they were saving for a critical Save vs. Instant Death.
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A lot of people around here also get incredibly superstitious about luck in their dice, and have all sorts of rituals around them. I've definitely encountered people who've gotten upset that someone rolled their die and let the luck out which they were saving for a critical Save vs. Instant Death.