If venting a dryer to the roof is the shortest distance are there any reasons this is a bad idea.
If you have to put in an elbow where it is not easily accessible then I would not do it.
Galvanized dusting straight up through the roof with a proper cap is the only way to do it.
The cap should be relatively easy to remove as you will have to clean the ducting at some point in the future. Best to clean it at least once every two years.
Also make sure the vent screen is good size or it will plug with lint here.
Be sure to use venting duct tape to seal the joints (if any) in the attic. You do not want a leak putting moist air into attic.
Also not a bad idea to insulate the pipe section in the attic.

Is snow an issue.
Not if you get a proper cap.

The main reason for not going through the roof is that if it does plug it is a royal pain in the you know what. But sometimes it is the only or the best venting option.

What do you mean, Galvanized dusting,,, this is not clear.
Ducting not dusting - my typo. Round metal ducting not that plastic or expandable tin foil crap.

I've not seen a roof jack that is capable of being removed for cleaning.
Then jiggery pokery one so that it is removable.
If you do not make provisions for taking it apart when you install it it will come back to bite you when/if it clogs up.