Working With Rails

Hello, I would like some advice on how to optimise my code.
I have different model

building has_many roles

role (which brings the type of role for the user for the building) belongs_to building belongs_to user

user has_many roles

And I have a lot of method in the building model to find the different type of member for a building
like

def find_admins_of

roles = self.roles

admins = []

for role in roles

admins << User.find(role.user_id) if role.role_type_id == Role::ADMIN

end

admins

end

This is not the best way to do it but I would like to know which better way.
I have thought of a
has_many, through but I can’t find the right syntax for the conditions on the role.role_type_id

I hope I am clear.

Thanks for your help
Nicolas