SQL Row Total with Pivot using Dynamic Columns

I have been researching and would like to use SQL's built in ROLLUP command on my data, but that has proven not to work for me. Any help would be greatly appreciated.

Here is the SQL pivot query I have created using Dynamic Columns. I want to add a Total column at the end that sums up the count.

DECLARE @SQL as VARCHAR(MAX)
DECLARE @Columns AS VARCHAR(MAX)

SELECT @Columns =
                            COALESCE(@Columns + ', ','') + QUOTENAME(order_date)
FROM
(
SELECT DISTINCT order_date, order_month
            FROM rpt_sales_performance
) AS B
ORDER BY B.order_month

SET @SQL = '
WITH PivotData AS
(
SELECT
                            order_date,
                            sales_person
FROM rpt_sales_performance
)

SELECT
            sales_person,
            ' + @Columns + '
FROM PivotData
PIVOT
(
            COUNT(order_date)
            FOR order_date
            IN (' + @Columns + ')
) AS PivotResult
ORDER BY sales_person'

EXEC (@SQL)