ROLLUP to calculate Month total for all Categories

Good Afternoon,

I have built a table with four columns: Period(Month), Category, Numerator, Denominator. Period(Month) is an Alias name, and Numerator and Denominator are calculated columns:

SELECT

,convert(NVARCHAR,Date,3) as 'Period(Month)'

,[Category]

, sum([X]) as 'Numerator'

,SUM([Y]) as 'Denominator'

FROM Tabl1

GROUP BY [Category], convert(NVARCHAR,Date,3),CAST(Date AS date)

ORDER BY convert(NVARCHAR,Date,3) desc

Now I want an additional record added at the end of all records for each 'Period(Month)' containing the total Numerators and Denominators for that month (but must NOT be broken down by Category totals within each month).

I assume that I need ROLLUP function for this purpose, but I was having problems ROLLUP in achieving the desired end result caused by 1) The Totals were being tallied for each Category for each month and 2) The 'Aliased' columns.

Kindly advise.