In Views, how can I show users with one role before all other users?
It looks like it's not possible with one View (Sort By User Role, Sort By User Role:  A New Idea?) which does kinda suck.

One option is to make two Views, one that filters on the user role you want at the top, and then one that filters OUT the user role.

Another option (this one would probably be easier to maintain) would be to create a field on the user accounts called Weight (you could hide it with Field Permissions), and then use Rules to populate that field with a high number for your chosen role when a user is created or edited, then you should be able to sort on that field.  If you do this though don't forget to create a second rule to remove/change the value in that field if the role is removed form a user.

tl;dr


Create Weight field on users 
When a user is created, fire off a rule that looks for a particular user role 
If it finds it, put a number in the Weight field 
Sort your view on the Weight field
Make an "opposite" rule to remove the Weight value on Role removal.
Profit