You should really do this as a callback in the user model:
User
after_create :build_profile
def build_profile
Profile.create(user: self) # Associations must be defined correctly for this syntax, avoids using ID's directly.
end
end
This will now always create a profile for a newly created user.
Your controller then gets simplified to:
def create
@user = User.new(user_params)
if @user.save
redirect_to root_url, :notice => "You have succesfully signed up!"
else
render "new"
end
end