According to :
Chris Lewis wrote:

Roxul is quite popular in Canada and I believe it's becoming
more popular in the US.

The R value is slightly higher than fiberglass (R21.5 vs R20 I
think for 5.5" batts).

It's heavier, and is a better sound barrier.

Sounds good. About the weight, I have standard 1/2" ceiling sheetrock.
Will the weight be an issue?

No. It's still mostly air ;-)

If I go with batts, it will be resting on
the wood beams which should be fine, but if I go with blown-in, then
the weight might rest on the ceiling. Just don't want a sagged
ceiling, not to mention this is an earthquake area. Ho much heavier is
it compare to fiberglass and cellulose?

Roxul is spun mining slag, fiberglass is spun glass. Slag is slighty
heavier than glass, and the fibers are fatter, but it's still mostly
air. A roxul batt is probably less than 50% heavier than a fiberglass
batt.

If I go with blown-in, how difficult will it be to move them aside to
do some work? I like the fire resistent and moisture resistent
property.

You just push it out of the way. Because of its higher weight and fiber
size it won't produce a vast cloud of flying fibers like fiberglass
does.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.