SELECT
e.EmployerName,
super_userCnt = ISNULL(x.super_userCnt, 0)
FROM dbo.mytableEmployer e
LEFT OUTER JOIN (
SELECT
employerName,
super_userCnt = COUNT(*)
FROM employerSuper_Users
WHERE [Role] = 'Super_User'
GROUP BY employerName
HAVING COUNT(*) > 1
) x ON e.EmployerName = x.employerName
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden