You need to know your numbers. To calculate your breakeven ROAS, you need to take all your production costs into consideration: shipment, manufacturing, materials, etc. These are referred to as the costs of goods sold or COGS.
Then, you need to calculate your profit margin:
Profit margin = Product selling price - COGS (cost of goods sold)
Finally, to calculate the breakeven ROAS, you can follow this formula:
Usually, you want your campaigns to have a higher ROAS than your breakeven point.