ROAS means Return on Ad Spend. It simply means the sales profits you are getting minus amazon advertising you are spending. There are several advertising and e-commerce portals such as Amazon PPC Advertising, Google Adwords, Bing Ads and Facebook Ads that you can figure out the ROAS.
The formula to calculate ROAS is Sales Revenue divided by Ad Spend
For example if Sales Revenue is $20,000, and your Ad Spend is $5,000
It would be $20,000 / Divided by / $5,000 = Equals $4 or 400% Percent Return!
There are efficient ways to calculate and increase RoAS and lowering ACoS (advertised cost of sale), the higher the ROAS will be. It all starts with Amazon Campaign Management, Keyword Analysis and building an efficient Brand Store to showcase your top products on Amazon.