Rolling Avg

nknishant , if you need row level avg 

Rolling 12 = CALCULATE(Average(Sales[Sales Amount]),DATESINPERIOD('Date'[Date],MAX('Date'[Date]),-12,MONTH))

if not 

Rolling 12 Avg = CALCULATE(Divide( sum(Sales[Sales Amount]) , distinctcount('Date'[Month Year]) ) ,DATESINPERIOD('Date'[Date],MAX('Date'[Date]),-12,MONTH))

or

Rolling 12 Avg = CALCULATE(Divide( sum(Sales[Sales Amount]) , countrows(sumamrize(Sales,'Date'[Month Year]) ) ,DATESINPERIOD('Date'[Date],MAX('Date'[Date]),-12,MONTH))

Hi,

Why do you not want to use the AVERAGEX() function?  Share some data to work with and show the expected result.